Even 150$ for such phone is a good price. And I don't like to buy any locked phones, I feel like being trapped by the provider.
You can unlock them easily for $15.
You might like the Galaxy Nexus though if that's your preference.
And yes, I'm very happy with the phone for $50. It actually worked out to $70 because of taxes and stuff.
The CM9 ROM is coming along very nicely. It's pretty much 100% stable but the camera still doesn't work. I have small children so I went back to a ROM called Peach Sunrise 2 and it's been great, although I do miss some of the smoothness of CM9.
I'm really hoping for CM10 (Jelly Bean) but it looks as though we will never have a working camera for these newer ROMs.