So, I finally joined the dark side by getting an Apple iPhone 3GS and.... I absolutely love it. It's nothing short of awesome.
Now that the iPhone support most of the features of ActiveSync for Exchange 2007/2010, I can say it's almost enterprise ready. I say "almost" because it still requires iTunes and it doesn't support all the ActiveSync policy features.
Even so, for me, it's a truly fabulous device that I can use as my phone, email device, music player and more. Oh, so much more. I love all the apps!
And best of all, it just plain works. No more tinkering in the Windows Mobile registry, trying new ROMS, etc. just to try to get it to work the way I want. The iPhone works -- right out of the box.
I highly recommend it.