Hardware compatibility is a problem, having a group of people all targeting one particular laptop to fix is worthwhile but isn't a great way to fix it. There are various laptops that can be pointed to if you're persuading someone buying a new laptop to install ubuntu (though which is poorly documented).

There are multiple problems, the main one is that windows is known, comes "free" and already installed when you buy a computer, is less of a risk and is good enough. Most people will know a "computer guy" who can help them with windows or be comfortable that they can pay someone otherwise.

Software is a bigger problem in some ways than hardware now (though the web is fixing this), note the effort Ubuntu are putting into the software centre, allowing paid for apps, proposing to relax the restrictions to get new software into Ubuntu, running app competitions and so forth.

Selling operating systems isn't easy, look at how long apple have toiled in the wilderness and they have linked hardware, loads of good will via ipod/iphone, billions in the bank and have managed to climb to something like 5%-10% market share.