there is really no need to use an ubuntu package.
you could add lenny and or sid repositories in your apt sources file and then use
AptPinning - Debian Wiki
so you can still keep your stable repositores. or if this is your personal desktop just upgrade to lenny and its as good as ubuntu I say. Certain things aren't customized but overall packages should be the same since ubuntu and debian aren't just similar, ubuntu is built off debian packages. as I have heard, ubuntu is basically debian unstable with its own customizations, but still debian.
so IMO, I wouldn't mix packages