Sorcha pretty much covered the waterfront as far as Canada is concerned too. Mostly they are crap built, although they can be quite comfortable depending on how you live.

We recently renovated and sold my departed father-in-law's mobile. Unlike most, It had tons of storage, was originally built in Alberta and was very well insulated, with an excellent floor plan. I was forbidden to call it a trailer when we had finished the work on it and had to refer to it as the "aluminum cottage". It didn't have the feel of a mobile home at all.

Parks vary, so if your considering living in one, check them out thoroughly first and if you are considering a used unit, have a competent, qualified (sometimes hard to find) building inspector go over it first.

There are some pics of the renovated interior of the "cottage" on my flickr site on the "Do you have Flickr?" thread.