I've heard positive things about Emerald Spas, and no negatives. But that means practically nothing. It means they're probably better than the Dreaded Thermospas or the Notorious Gulf Coast wonders, but that's about all.
Remember that there are supposed to be something like a hundred manufacturers of spas in the US, plus a bunch in Canada. It's what Michael Porter would call a "low market entry barrier business," meaning that a few tens of thousands of dollars can put you in the spa business. You need an oven, a vacuum former, a fiberglass chop gun, some lumber, an ad in the paper, and a line of credit with the plastic pipe and pump people.
I'm in the same place you are - just beginning my research. I'm starting to think it's gonna be a long haul!