I'm pessimist : some mobile OS (lack of) features are going to desktop OS. Look at last versions of Ubuntu (Unity optimized for tablets), MacOS with some iOS features, Windows 8 Metro, Android possible use in light netbooks/desktops, etc.

The newest rumors say that they have already secured 10 million Euros.

To be honest, I think the best way to implement multitasking is simply to have it N900 "like" - Applications can run in the background as needed, no specific limits on anything.

But I'd also add an OS-level 'suspend'/'resume' tool, just like kill -STOP does, and tie it to battery/screen events. For example:
1. When charging or plugged in, all apps can be running without limit.
2. When on a 'performance' profile, and more than 10% battery, same thing.
When on a 'general' profile, applications are paused when the screen turns off(or battery below 10%).
When on a 'powersave' profile, all application but the currently active one is paused, and if the screen turns off that is paused.
3. Below 10%, screen is force-dimmed and has a very quick timeout, and the only applications that will work are critical ones - Phone, Contacts, Alarm etc., which will prevent some rogue app draining the battery and an alarm or phone call not coming in.

This sort of thing would A, allow full multitasking, at the level demanded by the user - In *most* cases, a lot of apps can(and should be) paused when the screen turns off, and this will greatly increase battery life. Want to leave an app running for some reason? Set it to 'performance' mode.
You might also add specific battery-aware features to applications that could override these settings; for example an IRC client might be allowed to keep running with the screen off, though it should only do minimal work, keeping the server connection. All screen stuff would only be done with the screen on.

Also note that I see no reason to pause background apps with the screen on in most cases, as the majority of battery is used when the phone is *not* in use - 10 minutes at 10x power draw is still not a lot when compared to a week's standby time.

I will note that this could definitely be implemented on the N900 and likely the N9/N950 without too much issue; N900's already got dbus messaging for screen off/on, and I've already got scripts to pause/resume the browser when the screen's off... which works excellently.

What do you guys think?

it's not rumours, they have confirmed it in an interview:

I like this line of thinking.. how about tying this into homescreen abilities - UI people got any good suggestions?

One thing I've always wondered is to have some kind of visual feedback that a background application is 'running hot' (using a lot of resources)

Taking the N900 way of doing things to the next level and show resource use in the UI, you could change to colour of a task's window border in task switcher to show their stauts at a glance to show paused/busy/hot applications.

No Colour/Greyed Out - Paused
Green 1%-30%
Yellow 31%-60%
Red 61%-90%
Red-White Flashing 91%-100%

For further information you could hold your finger on a task for a right-click menu showing more information like RAM etc. Or you could change process priority or pause/resume applications, or change between power profiles for each app as previously suggested by RobbieThe1st.

I'd also add an option to switch between a list of visible/active appliations, and a list of background/non-visible processes.

This is basically exactly what I am proposing. Although maybe still further simplified: on battery things work as in iOS . Background apps are suspended, except for certain exceptions like GPS, task finishing, media play. When plugged in, full multitasking. This can be overridden, if desired. Possibly through 'developer mode'. For most users the simplified multitasking of iOS is more than enough on the road. Due to notifications and those exception cases, it pretty much feels like things are going on all the time anyway.

On a similar note, the phone app should always be resident and available, and be given the majority (if not all) cycles when a phone call comes in. I hate the situation where you're trying to answer a call but the device is so laggy you never manage to do so...

I've often thought about this too but I think it's also important to have an audible/vibration notification in the event that a process goes rogue whilst the screen is off.

One thing that I always think UI wise, and it is perfectly demonstrable with a direct fremantle/harmattan comparison is use speed vs customizability. The N9 is faster to use than the N900, but you can never make it your own. You always see that same boring home screen, and the inability to pin apps in multitasking makes it impossible to 'glance and go', using a MS terminology. WP7 has built on this with the live tiles, and harmattan has the (mostly unused) live icons.

On the other hand the widgets on the N900 are good enough but as much as I tried to cram all my shortcuts in a home screen and use it as a launcher (ie never go to the menu) it never worked. It was always easier to go to the menu. I had installed a new app and that was not on my launcher screen, or my launcher was 3-4 swipes away in unknown direction. Having numbers on the home screens didn't help much as it required thinking rather than muscle-memory.

i think that the idea of fremantle that the switcher is more important than the launcher is great and we should try to build on that. How could we make the launcher better? One idea is to create a design spec to encourage applications to fill their screen with a large status message/icon when backgrounded (see cuteTube for harmattan). Another idea is to have ghosts of the mostly used applications after the running ones. And of course pinning, which would allow to run applications at startup, and have them always display info, like widgets.
Pinching could be used to resize any window thumbnail seperately.

Another thing that is awesomely useful is switching between the latest two applications without needing to go to the switcher first. This could be implemented with a gesture like e.g. Two finger swipe, or pinch from outside.

Now the desktop should remain because everybody loves it. See the maemo 5 screenshot thread. It gives you the ability to make your device your own, and build your user experience of preference. But it should incorporate the launcher functionality in a useful and easy way so that we can get rid of the third UI layer. I find myself clicking the top left button in frementle random number of times until I get to the screen I intended. That shouldn't be like that, the user should know where he is going next without thinking. Maybe the solution is to keep the flat harmattan home interface and add the ability to add up to $INT widget home screens, using a vertical arrangement for those, so that launcher/switcher still remain 1 swipe away.

Lastly I thought of the events screen useless, and I filled it up with rss etc. only so that it's not empty/unused. Now I am addicted to it, and I don't believe any number of widgets can replace it. Events should be aggregated and not be scattered around one tweet here, 3 rss entries there and two facebook comments elsewhere. I want to check what happened, not what happened in a specific network. There is the $APP for that.

These are my thoughts about the perfect phone UX. M*e*o OS's came close to that but there is always room for improvement.

Thanks for reading.

problem is pc apps doesn't care to powersafe but on batterrypowered devices this is a MUST in some kind of way.