I used WP7 for over a year, wasnt bad.
Tried using WP8 recently, after having a Note 2 for about a year.
Nope. Nothing to make me go back. Not enough apps, no widgets, not enough customization (both in fun stuff like themes and practical stuff like settings), lack of regular updates, some things are impossible while the rest require multiple steps, just unacceptable all around.
1. What do widgets accomplish that tiles can't?
2. What do you mean, lack of updates? The first big one came one month in. The second was after about 9 months. Another is coming at about a year. The BIG update comes at about 15 months. WP8 is guaranteed 36 months of support, and I believe they said all device would be upgradeable to WP9. With Android, it can be rather hit-and-miss as to the longevity of support. The HTC Droid Incredible I got was done with support after about 12 months.
3. The potential for customization is definitely less than that of Android, but when you're not rooting the device, it's not that big of a deal.
Personally, I never cared for the page-and-grid styles of iOS and Android. The contiguous lists Windows Phone uses seem much more fluid, in my opinion. One thing I REALLY like with Windows Phone's app setup is the Games hub, just because it sorts the games out of the regular app list, preventing excessive clutter.
What is impossible or excessively difficult to do on Windows Phone though? I didn't do much with my Android device, but something I found out a couple of months back with my grandma's iPhone is that attaching things to texts or e-mails is obnoxious to do on iOS (not sure if 7 changed that). I can't think of one thing in Windows Phone where it has seemed to be more difficult than Android, except what someone else mentioned bout how awkwardly "sorted" the Setting menu is.