I use only Edge for internet access on my N900 with no Wifi, I noticed that by leaving my 2g internet connection off and manually connecting only when needed increases battery life dramatically. That means no widgets updating automatically and sadly no IM running throughout the day. It has however given me a large increase in battery life that I can use to browse the web etc.

Would have been nice to have msn running all day like I did with my e71 unfortunately I can only use pidgin to get on msn, the haze/butterfly telepathy doesn't connect for me. Using such an app dramatically reduces battery life even when idel.