The dialog boxes, the very vanilla looking rea plugins. it just doesn't feel polished like Sonar does.
Yeah, I have to agree with you there. There are some very unfinished parts to the GUI, so I avoid them! J/K. The ReaPlugins are by and large hideous to look at, but they by and large do what they're supposed to do.
It's a not-so-silly argument, IMO, about how important the GUI should be. I hear the "Why should it matter? Trust your ears" argument all the time, but it does for sure matter to most folks.
-Susan