[ylhert]

Preach! I do not understand this criticism at all. Rails scales just fine, in a web app it's the DB that's the bottleneck 99% of the time. Sure, the ORM can get you into hot water easily if you do dumb things (or just don't pay enough attention to N+1's etc), but one should be using the ORM wisely and deliberately, rather than living ignorantly of what's happening behind the scenes.