For WP7, I like the design, I like the .net development environment and it does what I want a phone to do. I generally find it more convenient than the I-Pod Touch and the "missing features" aren't things I personally can't live without (well, or I just use my I-Pod for them)
Just want to say that you can do iphone/android app dev in C# by using Monotouch/MonoDroid. Of course, you have to write a different UI layer for each platform.