My opinion will be slightly biased since I've been using an iPhone for roughly 18 hours, after coming from Android, which I used for the past 13 months. So far, I do really like the iPhone. The OS is obviously polished, everything is basically seamless, and it looks damn nice. I am, however, holding all final judgments until I've used it for 2-3 weeks.
Right now it's really too new to me to really say my ultimte opinion. It's slightly different than Android and somewhat (mildly) confusing, simply because I'm learning a completely new phone which does essentially the same things, only in a little different way. The few things I do not like are the notifications, and I know that will be changed come iOS5, but for the time being they suck. Android definitely has that one better. It's also easier to add downloaded ringtones. And personally, I like the browser on Android better, but only marginally. Other than that, so far, I don't see a ton of differences, just the average "I have to look in a different spot to get something accomplished" thing. To me, so far, there are a ton of similarities. And millions of reasons to love both.
That being said, if I (and this is just me) had an upgrade to blow right this second, I'd get the Bionic as long as my area had LTE. And for further disclosure, I have used two Motorola Android phones (Droid X, Droid 3) and an HTC Incredible 2. Or I'd wait to see what the iP5 has to offer next month, or the next batch of Android LTE phones in the coming months, and so on and so forth.