Rackspace-only fix in aocole:
Pull request submitted.
I have changed the 'knife rackspace server create' command to use the bootstrap subcommand rather than hard-coded bootstrapping scripts (that were debian-specific). I have verified this works with Rackspace and CentOS 5.4 (this also required updating the centos5-gems bootstrap template).
I'm going to mark the issue as resolved so it gets some attention. If this contribution looks good, please reopen the ticket, reassign to me, and I will complete the work for terramark and slicehost, and add the --bootstrap option as suggested in the comments.