Ask HN: Y Combinator vs. other incubators

I'm thinking of applying to YC summer 2010, but have also been looking at some of the other incubator programs. For example, Founder Institute has several sessions that will be running from December until April.

Is there any downside to attending another incubator program, then applying to YC for the summer? I know that many of these programs differ in philosophy (incubators of founders instead of companies, etc.), but is it a good idea to attend more than one of these programs, or would it be frowned upon?