MVC3 + code-first from the EF4 CTP makes throwing together proof-of-concept apps very fast (and painless!). You don't have to do much besides design your models and you get a functioning site to start with.
1. A technical bug - EF often fails to update SQL Server DB on model change (RecreateDatabaseIfModelChanges).
2. More general - the generated UI is completely data centric, while even MS people advocate for business centric, task based UIs.
As to the generated UI, it's pretty similar to what you get with Rails scaffolding. I haven't spent a ton of time with it so you may know better than me, but it's nice having the default views generated while wiring everything together and then changing the generated views to build something a little more useful (the same way you'd do with scaffolded Rails objects).
Or you could write the form itself with the "EditorFor" helper methods, either for the whole class or for each field. It's not perfect, but good enough for a quick prototype or first version.