I'm using Capistrano to deploy a moderately complex web application built with Rails and some custom frameworks. There are about 15 roles and 30 hosts in the deploy list. For some unknown compatibility issues with existing tasks, I am pinned to capistrano version 2.2.0.
This version of cap is buggy. It crashes 50% of the time during deployment, it crashes mid-task. The most troubling behavior are the inconsistencies in error states. For example, running the same task a second time after a first failure will "just work". I'm not comfortable documenting a process for others as "well, um, just run it again if it fails and you might get lucky. That's just the way it is." This leads to my question.
Upgrade or migrate?
As far as I understood, capistrano's instabilty in the main thing which bothers you. Upgrade should be easier than migration, therefore I'd recommend you to investigate 'unknown compatibility issues' and upgrade to the latest version. Then you can see whenever problem is gone.
However, looking at the alternatives is always good idea. Look at vlad, I've seen a lot of positive testimonials in ror-ru mailing list from developers of large russian ror sites.
Good luck.