I've been looking for a decent open source project manager for some time now and I keep almost finding what I want; but there's always one aspect that I could never live with - and it's too often the design. Most packages I've looked at have a design that looks like it came from the last century: sharp corners, a flat layout and/or no sense of color at all. Almost nothing is even remotely modern. And this doesn't just affect project management software, a big chunk of open source web software suffers in much the same way.
One reason perhaps, is that good design is so hard, it always takes several iterations to get a design "just right." And, if the infrastructure isn't built to handle design iterations easily (e.g. poor coding practices; such as hard coding the design rather than using templates, etc...) it become a tedious and error-prone process as well, leaving the internet with more than it's fair share of ugly (if functional) software.
It also probably has something to do with the fact that a CS degree doesn't really require any design courses and tends to spend far more time on the nuts and bolts of programming (i.e. how to write an algorithm) than it does emphasizing the interface. I think there would be a lot more good interfaces in existence if this was addressed. Say, require two to four classes in interface design and usability.
It's really a pity that there are only a few projects that really seem to get interface design, because it's definitely worth the extra effort.