The Darkroom app helps the camera in low light – it can detect camera shake and picks the right moment to press the shutter for you so the pics aren’t (quite so) blurry.
I’ve had my 3G iPhone since day 1 in July and it’s great. The contract price isn’t too bad if you use a reasonable amount of calls, texts and data. It includes wifi access on BT Openzone and thecloud too.
Battery life not a big issue – if you use it like a non-smartphone (ie. calls and texts) it lasts ages. Of course, regular use of 3G and wifi with heavy-duty apps on a big, bright screen will deplete the battery fairly fast.
There’s PAYG, but the upfront cost is quite steep. Hopefully now that there’s an unlock for the 3G one it will get secondhand prices (especially of the first, non-3G, iPhone) down a bit.
Or as said, if you just want the apps, music, video, wifi browsing stuff then get a Touch – they’ve been revised a couple of times so cheap ones often available from the apple refurb store or secondhand.