At the low-end, they've usually used some no-name distribution with nonstandard components and a skin that looks just like Windows at first glance. I think making it look like Windows is probably the worst thing they could do for user comfort; regardless of looks, they'll eventually run in to something that doesn't work like Windows. The experience is less jarring if it looks different from the start. Getting help from technical friends and relatives is definitely easier if it looks, feels and works like a popular distribution.

The low-end Linux machines usually aren't cheaper than Windows, and little explanation of the advantages that might matter to that market segment can be found in the marketing materials for such machines. The advantages as I see them are easy access to a large amount of free, safe software through the distribution's repository, and reduced maintenance relative to Windows; it doesn't become slow, get malware, etc... if you just use it without messing with anything.

There have been some really puzzling decisions at the high-end too. Dell's Ubuntu developer machine having the lowest available screen resolution comes to mind. Usually, when large computer manufacturers offer professional machines with Linux, it's hard to find them. There's usually a "customize this model" page that offers a choice of OS - any of several versions of Windows. The Linux versions are treated as separate products and not listed where the standard models are. People only find them if they're actively looking.

It almost seems like these ventures were set up to fail so PC manufacturers and/or Microsoft could say "Look. We keep trying and nobody buys these things.".