just like with _any_ other language, if you are not careful you can end up writing some sloppy RoR code.
especially once you get into the 50-100+ migrations apps - your first few might suck unless you have some good guidance on how to do the more advanced things.
as a corollary - I just joined a RoR startup and by the end of my first day I had already closed out 2-3 feature/bug tickets, mostly because the code was clean & well-structured. in some heavier environments I remember it taking a few days just to get your system setup & figuring out how to navigate / compile / etc. all the code.
Also, what would you recommend instead?