Windows Mobile with Mac OSX
Actually, I am one of the very few people who have a Windows Mobile 6.5 phone (an HTC Touch Pro 2) and I synch with my MacBook Pro using "missing synch".
I bought an iPhone 3G when it initially came out, but the functionality (back then) didn't support LogMeIn (which it does now) - which I absolutely required for work, and the bluetooth functionality was COMPLETELY nobbled. There were a couple of other things the iPhone couldn't match with the Windows Mobile platform (back then) - and still today, the iPhone doesn't have wireless tethering.
I also hated AT&T. My first bill was over $600. I switched back to sprint and argued my bill down to $200. They really tried to rip me off, and it wasted SO much time talking with them.
I still own my iPhone - I use it like an iTouch - with the benefit of the camera. I love it, and it now has far more than the Windows Mobile platform provides. But I got burnt by AT&T - so I'm waiting for the CDMA version. I could've got TMobile - but the speed of the network is VERY important.
However, my 3G iPad is awesome. I'm quite happy with the $20 or so per month for the AT&T data - but realistically my iPad and my iPhone works a LOT faster through my Sprint Touch Pro 2 when I'm wireless tethering.
I am VERY impressed that Microsoft has connectivity to the Mac though with their new phones. Proves that Microsoft is very wary not to alienate the market share that Apple has these days.
But, I'm not planning on getting Windows Mobile 7. I think Microsoft has missed the boat, and their new phone OS is going to tank. Only existing Windows Phone users "might" get the new phone - and theres not so many of them anymore.