It isn't so much that it isn't useful for devs, it is just that the devs we have favour functional over pretty. If it can be functional and pretty, great!
Also, Rockbox runs on many many more players than the Sansa, and we want Rockbox to look the same across all targets (within limits). Thus we aren't going to pick say the Sansa interface and apply it to all targets, we are going to have ourr interface on all targets. If someone wants to improve that interface great, but have a look at all the previous discussions on this first to see why that won't necessarily be easy!