I have been using an N900 for over a month now, and not experienced one single issue you mention. Take it from me, you have obviously been exposed to either an N900 with possibly a corrupt memory card fitted, or one that has early prototype firmware.

I have been running several applications at any one time, without any issues, no jerky side scrolling, in fact, mine has been smooth scrolling thoughout a couple of firmware changes.

Please do you homework before posting in future, as this thread is quite simply taking valuable time of members here who could be elsewhere within the forums, helping and advising other members who really know what they want out of the N900.