I too am a power business user. I had the iphone for less than a month but the lousy network service on AT&T was a severe problem. Also, it depends on what you use most. I rely on calendaring and notifications and the iPhone was terrible on both fronts.
I looked at options and bought an Omnia on Verizon. I hated the Omnia, WM 6.0 and Touchwiz. I only had that phone a week and there were LOTS of times I wanted to do my own wiz on that phone. I replaced it with a TP2. Really nice phone and I liked it quite a bit, but still WM 6.0, heavy and large from the added keyboard. Still, a very sturdy and nice phone but just not for me. I then replaced it with the Imagio. I've now had the Imagio for about 5 weeks and I'm liking it quite a bit.
The WM 6.5 with TouchFlo makes WM much more usable and finger friendly. WM is far from perfect but I can set it up fairly well to do what I need and to keep the items I use most handy. Its not a perfect phone but the things I like about it are the screen size, the phone size, the fact that what it doesn't do well there are utilities to make it do better. Also, I am loving that it is both CDMA and GSM. The phone is on Verizon, obviously, but I also have a prepaid TMO sim on the GSM side. I use Verizon for my family and very close friends, they are the only ones who have that number, and I use TMO through Google Voice for business so they only have the GV number.
Where you are and who offers the best service where you need it is a critical factor and on that one I can't help you. I've had em all, Sprint, TMO, AT&T and now Verizon. I'm in a very rural area and Verizon has them all beat to hell in terms of service here. That's great for me but you have to get one that works for you. No matter how good the phone it won't do you much good if it doesn't work well where and when you need it.
R