Damien Merenne has just announced a Bazaar-NG SCM module for SwitchTower. All you bzr users now have one less reason to not use SwitchTower.
Damien has given permission for this module to be included in the next SwitchTower release, too. If you’ve got a pet SCM that you’d like to see supported by SwitchTower, just take a look at Damien’s code to see how little it really takes to implement a new SCM module. Then, implement it and submit it as a patch to http://dev.rubyonrails.org/newticket.