Percona toolkit 2.1.9 is now available on Dotdeb for Debian 6.0 “Squeeze”. It includes many bug fixes and it is worth upgrading to, especially if you were affected by the backwards-incompatible changes to pt-heartbeat in 2.1.8. Take a look at this blog post by Daniel Nichter for more info.
As usual, please read the list of changes for Percona toolkit 2.1.9 before upgrading.