Haiku does some amazingly impressive things software-only, drag & drop and scroll really don't need hardware acceleration. If they do, there's a problem with your code.
Mind you, I can do real-time 1080p mp4 video scrubbing on haiku running on a thin client so...
I was thinking about it and the issue is really the "if there's no compatible hardware llvmpipe will just take care of it" attitude. If you watch these software rendered graphics carefully (or read the code) they make trade-offs that allow everything to work with low input latency and render in real time and sometimes that means "corrupt" looking graphics on the screen which the OpenGL style graphics won't generate (the frame is either done or it gets skipped.)
Mind you, I can do real-time 1080p mp4 video scrubbing on haiku running on a thin client so...