We recently updated filmamora.com to use the latest passenger (2.2.10) and Ruby Enterprise Edition 1.8.7. This was a move from 2.2.4 and 1.8.6 respectively. (We also upgraded to Nginx 0.7.4)
So far it seems to be a very worthwhile move! I had looked into using ruby 1.9, but ran into may issues with gems.
Here are some Munin charts.
Mysql... this I don't even understand! What a difference!
Memory - also seems to be a nice drop.
Individual Interupts
Interupts
The webapp itself was not changed at all. it is still using Rails 2.2.2.