After messing with an HTC HD7 in store, there's no question in my mind that IE for Win7 Phone is now the best non-iphone first-party browser in the mobile market. I might even go so far as to say it ties the iPhone browser for first. It pretty much looks and behaves just like it, with a few nice little additions.
The rest of the phone/OS seems pretty good, too, but I didn't really mess with it overmuch. Touch, panning, and zooming are all much more smooth and responsive than any android phone I've used. Web browser is the only thing that really matters to me, though.
Still, with both the handset and comparable plans costing about the same, I'd probably still go with an iPhone by default.