I have a Coverit temporary garage that I've used for almost 10 years now, and its a very satisfactory solution for the price. However, there are some caveats. First, they're not things of great beauty. I live on rural acreage, so this isn't an issue. Second, they're not secure - again not an issue for me, but people in more populous areas may be concerned. Third, how suitable they are will depend on your climate. I live in a semi-desert area with bone dry frozen air all winter, so the car doesn't suffer at all over the winter. If I lived in a damp place, it wouldn't be as good.
Still better than leaving it out under a tarp all winter!