Personally, I love my covermate3.. it has hydraulic assist for the lift making removal of the cover a one handed job that even my kids can do when there is 6 inches of snow and ice on the cover. It stays up in all wind that I have encountered, but it also has a very heavy duty wind lock that prevents it from closing in very high winds. Most of all, it is nearly flush to the hot tub and mounts just below the shell so that you can butt the tub up to a deck or whatever without having to worry about clearance.
The only downside is that the cover sits 2 or 3 feet above the level of the tub when open, but I actually like this as it blocks the wind from the west for me and provides that much more privacy.