For the people with the Not enough memory in target location error, please read the N900 Updates FAQ Sticky, see Q: It says I don't have enough memory, what do I do? or do the updating via Nokia Software Update.

As for this update, can't see any noticeable changes other than its performance; it's quite snappier, actually. I dunno what they did (removed temp files/cache?), but still, thumbs up for that one.