Asking the Lifehacker crowd may get an interesting reaction, but the responses seemed pretty skewed to tech savvy users who've already tried Linux. If you've already tried Linux, I can't imagine the look and feel was the reason you abandoned it. Hardware incompatibility, lack of software, etc... This is what the commenters noted and they probably don't even represent the average customer well. When I think of Linux, I think, "business, servers, incompatibility and geeky". If Ubuntu is looking to make big headway in the world of desktop computing, I don't think those associations serve them very well. Addressing the look and feel of the software may help to change the "geeky" impression, but certainly won't do much else for the others.
I wonder if the Ubuntu folks have tried just putting a bunch of Ubuntu computers in the hands of some current (average) Windows users or students. Load them up with the apps you think they need (office stuff, music software, etc...) and then let 'em run with it. Survey them afterwards and even if the information is skewed, you'll probably get a pretty good read on what some of the critical issues are. They might even tell you that the software just didn't feel cool enough, supporting the look and feel approach and totally shooting down my earlier assumptions. I can't imagine this would actually cost that much to try and at the least you'll probably get closer to discovering what the main problem is with using Linux for everyday computing life.