Battery life is amazing, I'd say with it clocked at 800mhz and with wi-fi on and browsing the internet you'd get at at least 7 hours, probably more like 8 or 9. With some more energy saving features, like wi-fi turned off, you can play games well over 10 hours, probably between 10 and 13. Personally I clock mine at 690mhz opp2 for normal use, but it's set to auto overclock up to 1ghz at opp5 if using something that needs it (like PSX emulator). Regardless, you are very unlikely to run out of battery power as long as you can charge it in the evening you should be able to use it most of the day.
Around the house, it's not too inconvenient to actually plug it in. Sometimes I remove the battery and just leave it plugged in, downloading my torrents and playing some music on my hi-fi, I suspect it's cheaper and more environmentally friendly than running either my intel I7 desktop, or my asus netbook.