Again, number of cores has nothing to do with it.

Nokia N8 - records perfectly, with a much larger sensor (12 megapixels) and much higher bit-rate compared to N9, and that gives much higher quality. But it has a slower processor, so it should lag like crazy .. should... but it doesn't. At all.

Nokia 808 Pureview - 41 megapixels - 1080p video.. on a single core CPU (which is almost the same as the N9 CPU).. records perfectly and with amazing detail and oh, no lag. Enough said.

Yes, the video lags while recording and it's annoying..

but

It's not the number of cores. It's the OS code which is not optimized properly because Nokia abandoned it. But for its first few iterations in just a year, it's pretty darn good (as opposed to iOS, which took 4 years to be anywhere near a productive state.. Or Android, which, after 5 years, RELIES on more and more cores to run smoothly since the code is that messed up)

Soooo, what we need is to pray that somehow miraculously we get a maintenance update which cleans out a few multi-tasking bugs and such.. and more GPU drivers + codecs for video playback.

In other words, I'm never gonna sell my awesome N8 :P