|Uses CSS based skins.. easy to use + create as well|
But the sad truth about the original mplayer is that, it is ugly as hell. Even with its GUI, still it is nowhere near the level of a professional looking GUI, trust me, that default skins come with it won't impress any of us. And on the other hand, there is actually nothing Mplayer can't do as a multimedia player. With a little help of the Terminal, MPlayer command-line version is a very powerful tool.
Play a huge number of (almost all the codecs) files right out of the box, highly durable (even reads damaged CD/DVD's without much of a hassle) and comes with lots of features. But as said, it "lacked" a really good looking GUI. That's where the UMPlayer comes to, it just fills that gap really well.
With its skinnable, sexy looking, fully featured GUI... I don't think even the QT based, SMPlayer have a chance of competing against it!.
So with it you can...
*. Play divx, xvid, mpeg 1/2, H264, H263, Real video, Quick time, Theora, WMV, FLV, AAC, Vorbis, MP3, FLAC, DTS, TrueAudio... these are A FEW TO NAME.
*. Various filters/effects -
This is one of the best things I love about MPlayer (UMP in this instance), it let's you adjust audio/video delays, enhance videos using various video filters, graphical equalizers, audio enhancements, Subtitle timing settings, etc.
*. Playlist support.
*. Search YouTube videos directly from the GUI
are just a few to mention. Although the UMP project seems to be new and according to Andrew, there are few bugs at the moment too. But as said this is well worth giving a try if you fancy an easy to use highly customizable, full featured cross platform (not just for Linux) multimedia player!.