I have a Galaxy S 3 and will be most likely getting an iPhone 5 as well.
I'm in no real hurry, so will wait to study the reviews before deciding anything - if the battery life isn't much better then I might not bother - but I expect it to be better.
I think the Galaxy S 3 is a brilliant - near flawless - phone, if you like Android. I do like Android but I don't use the more advanced features of it, my phone use - despite me buying many phones and fiddling with all aspects of them - is quite limited in reality. I mostly just browse, for which I think Safari is excellent, check things like Twitter and read various news apps. Obviously a good camera and video recording are important, too, as well as actual phone functions.
The more computer-like functions of Android are often lost on me. I don't need them, I actually quite enjoy the simplistic nature of iOS, that's what heavy phone use/tinkering will eventually do to some people. I'm just bored of it and want a nice simple interface. People often bring up the more fancy features - such as gaming with a PS3 controller on your phone, but usually as a stick to beat iOS with rather than them genuinely finding them useful. I certainly wouldn't find such things useful at all.
I also miss iOS apps, Android apps are generally fine but more than a fair share of them are ad-supported and many of them aren't well optimised for the top end phones, and feel like they're made for a cheaper phone - because they probably are. I also like the hassle-free, reliable nature of Apple's firmware updates.
I also think the design is in a different league, it's fantastic and I do enjoy a premium product. The S3 isn't badly made by any means, but it doesn't scream quality like the iPhone does.
I'll probably get a Lumia 920 as well, that looks to be a very impressive phone, but again, whether I go for it will be based on reviews, then I'll see which I settle with out of the three (S3/iP5/920).
The new LG phone on the horizon sounds very impressive but it's LG so will most likely be somewhat of a let-down overall. There's also the fact I use my iPad quite a lot and like the way the phone ties into it via iCloud/Photo Stream, etc.