m528/p1888w just isn't worth it imo. 2 hours battery life, the xp install is missing wifi and a few other things, and the shipped linux is a closed and limited distro.
I would pass.. If you want something to fit the needs that you listed, and still somewhat pocketable, i would go w/a used sony ux(basically a handheld laptop, but poor standard batt. life) or the N810 if you indeed want tons of apps/flexibility and great battery life.