You can see the list of original improvements here
It seems that this particular problem with mod-rails hanging after a few hours and taking down apache with it (I experienced this in an apache deployment that I tried personally … and its a bit scary) was part of the motivation behind the original mod_rails/Passenger Release Candidate.
Updating mod_rails to to 2.0 made all my problems go away (mod_rails also had some trouble interacting with the soap4r plugin), but this update has even more fixes.
I have a site running on mod_rails that was formerly served up using 3 mongrels in a cluster and it runs a bit faster than before, but deployment and application management is obviously MUCH less of a headache.
These guys are doing something for Ruby on Rails, that I don’t think many understand the implication of, but cannot be overstated. Big cheers to the guys at Phusion!