I got mind at citicall and the guys there are nice since I got my bricked N900 returned anew (they wouldn't be so nice if they knew the reason of bricking...well anyway).

I overclocked it....and that's pretty much the only interesting thing I've been doing since. The others are just as usual, like running apps and games and develop stuffs on it. XD

The eMMC is the internal flash mapped under your home (/home/user/MyDocs), and it's the visible drive (N900) when you use your phone as mass storage device via USB. The contacts and stuffs are saved in this flash drive. Therefore if you reflash the eMMC your phone will return to default.

I'd recommend you to reflash the eMMC as it's a new format. Upstairs there're people confirmed that the new week 19 rom runs fine without reflashing eMMC, anyway, your preference.

Of course, you must backup your eMMC before reflashing it, but I'm sure you wouldn't need to be told of this. ^^