[d0m]

I would go with UI improvement. I feel like linux has always been "ugly" visually.. even from its first years with red/blue dialog in console. Linux hackers just seem not to care about UI as much as designer would.

Without being harsh, when someone used with Windows or Mac look at Ubuntu, it always look a little "goofy" or "quickly done". Of course, they don't know the beauty of unix, how files are the main part and so important or how configurable everything is. The only thing they see is "A weird kind of Windows that isn't as pretty".

But then, who is your main target audience? Are you trying to make windows/mac newbies switch to Ubuntu? I say that because, if it was only for me, I'd say the best thing you could "add" to ubuntu is to remove all the extra stuff and keep in minimalist. (Warning: I use archlinux with fluxbox). I guess it all depends of your audience. But if I get it right and I'm not really your target audience, working on the UI would be the next big thing.