"Long startup times or not, sounds like you should probably be using autotest or watchr. 20-30 seconds is not normal. Unless the app has a massive amount of code and dependencies, that sounds like an environment issue."
Autotest helps some, but 20-30 seconds is pretty standard fare. Maybe I use too many gems, but I don't think I should forgo reusing community code to reduce start times.
Maybe it's unfair to make a generalization about "rubyists," but it seems people in the community get overly excited about something that saves 5 characters in their codebase or makes something readable to non-devs (for all those non-devs who will read your code.
Another example - the ubiquity of DelayedJob. The standard usage is to insert delay into your call chain, so foo.delay.send_emails instead of foo.send_emails. This pollutes the ENTIRE object space with the method delay, in addition to the fact that it doesn't work well on many objects. I complained about this practice and the response was that it was clearly better to write foo.delay.send_emails instead of Delayed.add_job(foo, :send_emails) or something. For me, I find any pollution of namespace where conflict is possible highly questionable, although sometimes it's ok.
Metawhere adds methods like .eq and .lt to Symbol (symbol is something like an intern string, e.g. :foo or 'foo in Python).