Mine worked FANTASTIC in my garage. I had an oversized 100kBTU unit that I set at 45*F during the winter and kicked it up to 55*F when I wanted to work. As long as you set it up high in the corner aimed at a 45, all should be well. Those that have shade issues or intense heat issues are likely not using them correctly.
You have to remember these heaters are meant to heat up the concrete and all objects in the shop...and as such, if used properly all shaded areas should be just as warm as the rest of the shop. The only time those areas will be somewhat cooler is when the heater is on and cranking out the heat...but at that point it should be only maintaining the room temperature and any shaded area should be only slightly cooler. Once the objects area heated up again, so are the shaded areas.
Also worth mentioning, I can work within several feet of my 100k BTU heater without harm. Sure, it get's a bit toasty...but it's not uncomfortable in the least bit.
Here is my setup (my ceilings are 10'6").