AppHarbor is fantastic. I can't stress this enough. I've deployed three MVC3 applications on there already and they work effortlessly.

My workflow is:

1. Write code on dev machine.

2. hg push to BitBucket.

3. AppHarbor hook reads new push from BitBucket and compiled on their service.

Simple quick and easy deployment!

Once thing I wish they would offer is free domains like Heroku does. Hopefully this is a feature they enable in the future.