I waited a while to report this since I don't use my tablet that much but I think (and I may be wrong) that the SSU reduces battery life.
I have to say that I never had great battery life with my n800: when it was new I got max. 2 hours of use, now, with a non OEM battery, I have around one hour.
Top doesn't reveal any evident cpu hog
Of course it could be that the battery has deteriorated further, but the drop in capacity happened right after installing the SSU.