I dunno, I've stuck with Capistrano... I've used Vlad, but Cap just works and it only needs to be as complicated as you make it. My cap files are usually about 40 lines total and that often includes a section where I write the database.yml on the fly to the server. I've used all the other options, and they're nice, but Cap works nicely still.
Vlad's not bad. There's a similar project called Fezzik that I use extensively for non-Rails projects. Neither is as good as Capistrano if you're deploying a Rails project.
we are using vlad instead of capistrano and are very happy with it. it is much simpler conceptually. Also from several projects that I converted from capistrano to vlad it runs much much faster for the standard deployment process. I'm not sure what is the reason as I didn't investigate it much.
we have custom vlad plugins for usual rails related stuff, so our config/deploy.rb scripts are usually about 5-10 lines long. see https://github.com/astrails/vladify