Lots of issues with this of course and many of them well documented. The iPhoneBlog, possibly the best iPhone site in my view, have reported on this down the months quite extensively. For me, up until the 2.2 update I had no concerns if I turned off 3g and just went with EDGE when out and about or relied on wifi at home to do most of my downloading.
However, things have been not quite so good since I set up "push" email and calendar/contact support via my mobileme account. This push facility is a well known battery drainer and it has been affecting me too but I like it so will just have to accept it. I have however turned off that "location' setting and things have improved since then, quite dramatically actually. I've also dimmed the brightness slightly and that too has improved things markedly.
I've been impressed hugely with the HandBase iPhone application which I have found to be easy to use, after a bit, and stable. Having a bigger screen adds to the usefulness of apps like this. I have however been struggling to get databases created elsewhere added onto it and that is something I need to learn sooner rather than later. There is a mac desktop but it doesn't seem to offer much except the ability to view files on it? It doesn't appear to offer any wifi syncing either nor the ability to create new databases or perhaps I am missing something basic.
Handbase is a powerful bit of software that can be used for creating basic stuff like simple checklists for shopping or todos all the way up to pretty heavy duty databases. I'm still struggling how to work out how to link different fields in different databases together as that would be useful. I've already got he windows pc desktop application at work which is great for creating new files but getting them onto the iPhone in a less than convoluted fashion is escaping me at present.