Yeah, I'm another Android user/owner who will very likely make the change. The Wifey is already using an iPhone 4, so I've had plenty of hands on with it, and know the good/bad/ugly (plus we have an iPad).
My Android experience has been mediocre. I've owned a Captivate and an Atrix and fooled around pretty extensively with several different products from HTC, Samsung, Moto ... and I've flashed CMx, Cog, different radios/BT stacks, done GPS tweaks, all in an effort to create a consistent, hassle free phone experience.
FWIW, I've been hacking around with phones/electronics for 20+ years, and am currently prototyping a couple of apps to extend some of our Enterprise solutions (Android and iOS). I'm very agnostic with technology, right around the World HQ here I've got Windows (desktop and servers), Linux, OSX.
The Atrix had very good battery, but a Pentile based display with so-so color/contrast, a mediocre camera, the Captivate of course has a dysfunctional GPS (after two hardware swaps and countless tweaks). Both had email issues with my configuration, requiring me to first deal with K9 and later upgrade to a pay app (Touchdown). I've run all the typical enhancements like LP/ADW (pay versions) and played around with things like widget locker. It's kind of fun.
... but at some point all the tweaking, and widget install/de-install, re-re-flashing, becomes tedious and you just want a device that you pick up and use - that has a high degree of availability (whether that's a factor of battery, app stability), etc. That Android phones expose the filesystem or score X amount on a benchmarks or can make an icon out of a bitmap becomes less important vs. a seamless, hassle free experience.
The SGS II is a pretty outstanding piece of hardware, overcomes several of the hardware issues (though still plenty of GPS, WiFi, and other problems being reporting ...). It's due at AT&T on Oct 2nd, so I'll wait and see how things pan out with Apple, but I'm 95% sure at this point, I'm headed to an iPhone.