Although I like the PC-like features of my Windows 7 Phone, the actual phone part isn't all that great. As of recently, the phone part stopped working entirely!
People were telling me that they tried calling but I didn't answer when I knew darn well I was available. Sure enough, I tried calling my phone from a different phone and it never picked-up even though it said I had three bars of reception. I was also noticing that I often had no bars of reception. A restart of the phone would get some reception again, but it was hit-or-miss as to whether I could receive calls or even make them.
I eventually called AT&T and they determined the phone was defective. Contrary to all the negative comments I've read about AT&T support online, I found their support to be very good. I had no wait to speak to a real person and within a matter of minutes, they had me setup for a RMA to get a new phone shipped to me. Apparently the phone has a one year warranty, of which I'm now thankful for as I'm not willing to shell-out over $400 for a new phone.
The AT&T RMA process is very well done. They sent me a box with a bare-bones phone (i.e., they sent just the phone body with no cover, no battery, etc.) I swapped-out your broken phone with the new one, put the old one back in the box it came in, stuck the return label on the box, and put it back in the mail. The only negative part about the whole experience is that the phone was shipped via the United States Postal Service which means it took forever to get to my house. The USPS shipping was free and AT&T did offer express shipping for a small fee, so I can only blame myself for having to wait so long.