I have been thinking about applying into a CRNA program here in NYC at Columbia. After I talked to the nursing department, this is what they told me. The minimum requirements for GPA are a 3.0. Minimum of one year working in critical care. However, to be competitive, she suggested NO LESS THAN 3 years. She made it clear that the RN's applying to the CRNA program, usually had no less than 3 years of critical care under their belt. She also said the GRE scores they receive, are some of the highest. CRNA programs are highly competitive throughout the US. There aren't very many of them, so your best ammunition is to get into crtical care (wherever) and work for a minimum of two years and get high GRE scores. She also said that working an additional year can sometimes work in your favor.
It is true that your GPA doesn't hold that high of a weight in comparision to your GRE scores and your critical care time in the hospital.
I also heard that the CRNA program will be a Ph.D program soon. I'm not sure if that is true, but a friend of mine who is a CRNA in San Francisco mentioned it to me before I started nursing school.
I hope that helps.