Quoted for truth.

@Dennis:
Just try firefox-esr under Easy Debian Jessie and you'll see, that it's unbearably slow (if it starts at all, that is).
Tbh I haven't tried Firefox/Iceweasel under ED since Wheezy, but even then it was nigh unusable.
The "Quantum update" was mainly about parallelizing things, which is great on a modern x86 PC with umpteen cores, but useless on a single-core Cortex A8.
On my EEE 901 netbook I see basically no speed improvement, because all the puny Atom N270 has to offer in terms of parallelizing is hyperthreading of a single core. What I see is, that now both threads are running at 100% for a minute instead of one, until the GUI is loaded.

I'm surprised the N900's watchdog doesn't keep rebooting the system every five minutes (RD mode on?).
When I started toying around with Easy Debian I pretty soon decided that I wouldn't compile on the N900. But I also was too lazy to properly learn how to cross-compile. Qemu was unbearably slow (even on my i7-2700k it was slower than on the N900), so I decided to buy a Cubieboard 2.

Edit:
Wait a second, I believe this actually IS the watchdog: