I'm a current iPhone user who really really really wants the Lumia 900. I stop by the AT&T store in my town several times per week to play with the demo units. Man, that thing is slick. What's kept me from pulling the trigger is the fact that I'm a current Sprint user (I'd move the entire family plan to AT&T in a heartbeat though) and I'm a Mac user. Obviously it's ridiculous to expect a WP phone to sync to a Mac computer with the same level of ease and integration as an iPhone, but with just a bit more sync support I'd give it a try.
I was playing with the Lumia (yet again!) and noticed the calendar app is pretty lame. The monthly view is too small to see any detail, and it doesn't respond to gestures like the pinch/expand finger maneuver. And there is no weekly view? Or did I just miss this view?
No, you didn't miss it. The calendar in WP needs a little TLC. I don't use view by week anyway so it's not really an issue for me. What I do is turn the calendar to landscape mode when i need a slightly bigger view. I have my calendar app default to agenda view anyway because I just find it easier to scroll up and down to see my appointments.