Where to start in no particular order...BlackBerry 8800, 9530, 9550, 9650, 9930. Palm Pre2 (twice). HTC ThunderBolt, Motorola Droid X, RAZR. HTC Trophy. iPhone 4 and 4S (current).
I really liked WP7 on the Trophy, but the failing was more hardware related, battery life. I miss LTE from the ThunderBolt and Sense, I miss BB quality email and messaging and I really miss the quality notifications of webOS...sigh...
If Verizon gets some high end WP7 gear this year (with 32GB+ of memory), I will definitely look at picking one up. I liked the overall performance of WP7, some issues I had were notifications, and the ultra-reliance on the cloud for its integration took some getting used to. The user experience is a wholesale departure from other platforms, but that's part of its appeal I think.
With AT&T's pricing of the Lumia at $99, that's going to offer quite an incentive to people who are wondering about spending $199, $249, $299, $399 for an Android or iOS device. It's a good recipe.