Joel Spolsky has been playing with Ruby on Rails. He's written about some of the problems that he found. This has upset some members of the Rails community.
On of the best points that Spolsky makes is one I've mentioned here before - the fact that ActiveRecord is a horribly crippled ORM system - it seems to have been written by people who are afraid to let their database do what it does best (i.e. deal with data).
Update: As Mike points out below, the article wasn't written by Joel Spolsky, but by an anonymous contributor to the "Joel on Software" discussion boards. Apologies for any confusion caused.
Update: Oh look. these people saw my error and spent an amusing hour or so taking the piss out of me. Glad I amused them so much.
That was a user, not Joel himself.
Well, I was paraphrasing (heavily, I admit) but I think that's what the whole of Joel's first section boils down to :)
Update: Ah. Right. I see what you mean. Yeah. I'll change it.