I've got a small tractor I'm keeping this winter in one of the $199 ShelterLogic units. I did a fair amount of research, and it strikes me that most complaints are based on people who didn't anchor them, didn't properly measure to set them up, and didn't keep the snow off. I bought extra stakes and have every pole staked down, and so far in our fall winds it's stayed put, but I did recently re-adjust the tension. They'll hold a little bit of snow but are definitely NOT rated for it. ShelterLogic does make snow-rated covers, but they are a significant upgrade and general require a special order; I figured by the time I was spending that much money I might as well do a real structure. I also considered painting the outside with FlexSeal to keep the UV light from destroying the material over time, but I read a story about a guy who did just that and it only made the snow accumulation worse since it wouldn't slide off at all, and it ended up getting brittle and cracking in the winter which damaged the tarp anyway.
People I've spoken to who use the Costco ones say to expect replacing the tarp every year. I saved $50 over the Costco one because I just wanted the one opening whereas the Costco version has several, plus the awning, etc. I figure if this one fails this winter or if I need to replace the tarp next year, I'll spend another $199 at Home Depot and add in the additional frame-supports to my existing structure. At some point I may decide to take the approach that Randyzzz did as well by adding roof sheathing (until I get to the point of being able to afford an actual structure for this thing).