I bought a Windows Phone the day they became available. Mine is a Samsung Focus, and I love the design of the phone and the look and feel of the Windows operating system. But since the day I bought it I have also had variety of power-related issues with it. Sometimes the phone just spontaneously reboots. Sometimes after such reboots, it will have lost changes to the settings, start screen, etc. But if I reboot again, everything comes back as expected. When I bought the phone, I did not install the optional SD card, on which some people are blaming the power problems with the phones. Even without the card though, I still had some issues--but not the reboot problem. Mostly, sometimes it would just seem to be powered off, and pressing the power button didn't turn it back on. At first I was having to pop the battery out and reinsert it, then power the phone back on. Then I discovered that if I held the power button in for about 10 seconds, then released it, then pressed it again as if to turn the phone on, it would power back on.
So after using the phone almost constantly for about 2 weeks I bought a Sandisk Micro SD card, 32gb. I had read the docs and backed the phone up before inserting it. I installed the card and performed the system reset. Then I synced. I was surprised to find that the sync reinstalled music, but not my apps. Each app had to be manually reinstalled from the marketplace. (I did not have to pay for apps again--the store knew I had already bought them). The sync also didn't restore start menu and settings changes, or Internet favorites. But after installing the SD card, I have now begun to see the phone reboot for no apparent reason.
So, it would be a great phone if the power issues can be fixed. But the sync system needs to be changed so that syncing a phone restores it completely, including apps, settings, favorites, etc.
I'm keeping mine just as is for now. Part of being one of the first customers to get one is the adventure of unexpected "features." But I expect to see Samsung and Microsoft working hard to address these issues promptly, and I'll be dumping my Windows phone if that doesn't happen.