Think of it in terms of what will attract current smartphone users. Android lovers won’t like it because it can’t take an SD card, comes only on high-end devices, can’t copy/paste and will likely never freely allow multitasking.
Does it have anything over the iPhone from this list? Zune Pass? Get real. Integration with XBox Live? Maybe for the hard-core Microsofties. I have no desire to integrate my XBox Live account with my phone.
Basically, it has many of the same complaints as are made against the iPhone, and no real benefits over it. Well, except for one, you will be able to get WP7 from multiple hardware vendors on probably all carriers.
Here’s a good fair review...it appears there is more than just xbox integration to win people over.
http://www.gsmarena.com/windows_phone_7-review-521.php
More than anything else, this would be the killer for me. It's one of my biggest beefs with the iPad, is that you have to jump through all kinds of hoops to attach external storage.
Screw that. I like being able to pop out an SD (or microSD) and either take stuff off, put stuff on, or swap it out for another one.