Ruby Debug is impossible to get working in 1.9.3. The maintainer of ruby-debug has gone AWOL so we're forced to deal with solutions like this http://blog.wyeworks.com/2011/11/1/ruby-1-9-3-and-ruby-debug that don't work within bundler or a team environment.
1.9.2 + Rails 3.x is attrociously slow (30+sec). With falcon (a very unstable ruby hack) the startup speed goes to 10seconds. But 10sec is still way too slow
Sorry, it sounds bad when I just rant. In the grand of scheme of things, Rails makes me more productive as a web dev than I ever thought possible. It's just easy to pull out the daily frustrations and complain. I've been trying to help fix these issues but they are so dependent on a web of gem authors, and core ruby fixes that it takes an extraordinary amount of time.
I'm almost to the point where I think things need to be fixed top down. Matz needs to take control and try to make stuff not suck as soon as possible. Since he's working for Heroku now, it's in his best interest to push the platform and keep new users engaged.