Yeah, I second that. While Umplayer is largely a Smplayer derivative, it has some nice new features such as good support for mplayer2 and (apparently) vdpau (tried using Smplayer and Umplayer with the same mplayer2 backend. Smplayer was installed from Ubuntu's repository) and Youtube viewer. It also looks very modern and polished.
![Mr. Green :mrgreen:](./images/smilies/icon_mrgreen.gif)
For the period of time when Smplayer seems to have stopped developing I have switched to Umplayer as my main mplayer frontend, it would be nice if some of the enhancements can be incorporated back into upstream if feasible.
As for the QT requirement, I think most recent Linux distros would be more than adequate. Even Ubuntu 10.04 comes with qt4.6.3 and can be updated to qt7 by adding the kde backport repo. I think it must have made it into even Debian stable by now.