Single-staff/part playback
It would be amazing to not have to open the mixer and select "solo" every time I want to hear an individual part played. I want to be able to select an individual part or group of parts and hear isolated playback directly from the score. Sibelius (I think) has a feature similar to this, and although Sibelius is a design travesty, that feature is one that many would enjoy seeing in MuseScore.
Comments
This is indeed possible in MS. Once you have created your parts, you have the option (via the mixer) to play only the displayed parts or the entire score. (Check-box in the upper-left corner of the mixer. It is really good to have this flexibility. Sometimes I want to hear only the part I am editing, while other times I want to be able to visually focus on the part whilst hearing the entire score.