My problem with the current design is that gabest willfully limited himself to MS's bad original design and hamstrung the ability to make a somewhat better UI. Not that I particularly think later WMPs were any better, most were worse, but being less ugly than the leading competition shouldn't be the end of the line. There are both major and minor things I've never liked about the old-fashioned interface, but none are really enough to get me working on it, so I guess they can't be that bad.
You can make a great looking player without compromising the simplicity and light weight of MPC - I would point to GOM player as an example. (Unless you really hate orange, but don't tell Andrei Herasimchuk that.)