I may as well chime in and say its not always that people are unsatisfied with what is out there; it can be because they simply want to do it themselves even if their offering doesn't do a whole lot different.
I can say that developing my own mac front end has increased my programming knowledge and skill more than 10 fold and will look pretty decent on a resume considering how many different bases a front end covers on top of covering some bases I never even knew of ;). since I want to be a mac developer obviously it was in my best interest to make my own front end using mac development tools and frameworks (plus i don't know jack about coding in linux, and honestly don't even know c++ that well, I'm pretty much straight Ojb-C)
I do agree with the philosophy that the OS itself should be the "front end" and that the only reasonable way to do that is through linux, but since most devs here don't know jack about programming for linux we are stuck with alternatives, but those alternatives work very well us.
Just out of curiosity what kind of "new things" could/should these windows front ends be bringing to the table?