I honestly would like to see better app intagration, I allready use a few and am trying to learn Houdini, so trying to keep track of Modo, Maya, LightWave, Shake, RenderMan, final cut and the rest, and then having to learn more UI, its a bit boggeling. I think it would be nice if maya users could just switch between MentalRay or Default to M~R or have it setup like RenderMan pro server and Artist Tools. Better texture representation in the maya UI would be nice too, granted that proablly will never happen because MentalRay still has issues.
Studio is a cool idea, and i can see its use, but it isnt always necessary, if its app intagration was better studio would be moot, but Studio, if improved, can be really cool. It would be like how MotionBuilder is for animation, but for rendering.
So i guess my wish list is
a working linux version
tighter intagration with host apps
a 64bit build of the renderer
i like Xlars's idead for navigation and shortcuts, being able to say ok Maxwell studio, you will have Maya's keyboard shortcuts, would be very nice, that helped me learn Modo alot faster.
better online documentation
possiable GPU support(i know this is a big if but hey, its a wish list)
and a personal one for me, my license to work again.