I like them.
Several of the water front homes I take care of have monitors in the garages . I find them very safe, quiet, efficiant and dependable.
I have been told that the new ones aren't made with the quality of the old ones. ( but then what is )
Depending on the size of your garage and how well it is insulated, it should / could do a very good job. I would suspect that in a working garage / shop enviroment ( dust dirt etc) A good blowing out with an airhose on a regular basis would be a good idea along with a normal seasonal cleaning.