One of the biggest failures I found starting in Rails was the lack of a standard for hosting. In the mod_perl or php world, the standard apache distribution has everything needed built in to the standard distribution, and you’d be hard pressed to find a hosting system (of any size) that doesn’t have them.
Rails on the other hand, seemed to have a boatload of ways to serve itself. There doesn’t seem to be a “standard” webserver. You have mongrel, nginx, phusion passenger (mod_rails), lighttp… the list goes on. And it doesn’t seem that there’s an accepted “proper” way to do the webserving yet. Maybe it’s a case of different tools for different cases, maybe it’s just a symptom of a system that’s relatively young (compared to the apache/perl/php world).