I like it as a phone.... But it's a bit boring. My old WM 6.5 phone had so many things that you could just get lost in playing\tinkering with, and Android phones are the same way. Conversely, WM7 seems fairly rigid and un-customizable. In particular, the lack of custom ringtones irritates me. Also the lack of cut and paste. And some of the app load times are ridiculous.
I haven't had any problem with data. I'm 1 day away from the end of my billing cycle and I've only used 200mb out of 2gb.
WP7 wasn't built to compete with Android, period. It's taken a complete 180 from where WM6.5 was and is designed to compete with iOS. There's a counterpart to everything Apple has, except hardware exclusivity. I think that's where it's strength lies. This allows it to spread to all carriers, and on a multitude of devices. With the hardware restrictions in place, performance should be similar across all devices. You have a desktop music/app management that is superior to iTunes (at least on Windows machines) and has Zune Pass. You have an established game client base that takes considerable interest in the phone as a mobile game platform, along with social integration that no one else can compete with. On top of that, include the Exchange integration that can be done because it's MS, and you have serious potential.
But it's just that - potential. MS needed to get the phone out, and what most of us early adopters have is something stuck between iOS and well, jack shit. Except I have better hardware, and what I feel is a better base OS. Yes, some features are missing - but MS has said they are coming, and we've seen video proof. It'll take time, but we'll see things come out just like we did for iOS and Android.