Seems like everyone nowadays is jumping to the Samsung Galaxy's, the few that have jumped across from iPhones to them, seem to be raving about them being "so much better" (including my mate Robbie, who is on here, and used to be a hardened iOS fanboi, constantly telling me to get an iPhone lol) - now I don't know how they are better, apart from the being different (Android as opposed to iOS of course).
Essentially though, they are running Android, and personally, when I was Android on my TP2, I really liked it, found it very useful etc, the only downer for me was the battery life was max 12 hours, but as it was an unofficial ROM (Android not supposed to be available on my phone, though it shares the same chipset/hardware as a lot o the older HTC android phones) that could be the reason.
Having used my managers Galaxy a few times, and watching Mark using his yesterday, they seem to flow really nicely and their feature-set is ultra impressive.
My ideal choice, would probably be a Pre3 or a HTC Pro7/HD7, but they are different OS's and thinking outside the box, but go into a shop, and have a good play with all the phones you are interested in, the o2 shop dos real phones, not just dummies, so that would be a good place to start. I'm sticking with my current phone for the time-being though, as yo know, WinMo is dead lol.
You should also be able to ask for demo phones. The problem with recommendations, is unless you have used all the phones in a certain market sector, each for a period of time, the topic is very subjective.
At the end of the day, if iOS is doing everything yo need it to (like me with WinMo), no real need to change; maybe upgrade to an iPhone 4? However, if there is features you see on other OS's or phones that interest you, not currently available on iOS, then you have to consider which phone and OS suits your needs best.