When MuseScore first came out, I think a lot of people knew it was going to be great.
And it is. It's also getting better all the time.
One thing that wasn't great initially was the Lilypond export. But MuseScore version 1.0's Lilypond export seems really good from initial experiments I've done.
And let's face it – that's the holy grail of music notation: a GUI score editor with good Lilypond export … AND MusicXML support … and command line options.
So in other words, a one-stop shop for music notation that supports the best tool (Lilypond) for output in terms of aesthetics and the more widely supported XML format in MusicXML … as well as those command line options for using on a server.
Well, well done people.
Keep it up.