Upgrading/switching from SwitchTower to Capistrano is easy if you follow this recipe (for linux):
sudo gem uninstall switchtower (remove all versions)
sudo gem install capistrano
And for each of your projects:
cap -A . # don’t forget the period, and keep your deploy.rb
rm lib/tasks/switchtower.rake
svn rm lib/tasks/switchtower.rake
svn add lib/tasks/capistrano.rake
svn commit -m “Capistrano upgrade”