I love the 3.1 rcs but using 3rd party css files that reference images are kind of painful to deal with in conjunction with the asset pipeline. I find myself making awkward directory structures in the vendor directory to avoid making modifications to 3rd party css libraries (like jQuery UI). I'm hoping a lot of this will go away when those things are packed into gems that I can just put in my Gemfile and forget. I'm sure Compass and Blueprint will get to that point pretty quickly but I'm not sure that something custom-generated like by jQuery UI ThemeRoller will ever be smooth to set up.