I too just bought one and tried it. I thought for the price, and Costo's return policy, why not. I just installed a Toto Aquia III in my master bath last week so had a high quality dual flush pot to compare to.
The costco unit was every bit as nicely fired and finished as the Toto. I stuck my fingers in the outlet and it appears to be fully glazed. As mentioned, it has everything in the box, including a new faucet and SS braided hose, brass floor bolts and neat chrome caps. The flush tower looks almost the same as the one in the Toto, slightly different but of the same quality and it has a fluidmaster fill valve. Hooked it up and turned on the water and it filled quickly and I was amazed how large the water spot was. Given the Toto has almost none, this one is huge. I first tried the half flush and it quietly and quickly flushed as it should. Later got to try the full flush and it worked perfect on the first try. Not to say this pot is better than or as good as the Toto but I can buy two for what the Toto cost and I had two more pots to change. Only thing it is low, like a regular toilet not high like the Toto which is ADA height. Oh and the included seat is only "so-so". It works okay, but isn't very sturdy. It sells for $169.99 in Austin TX, which is amazing for what you get. Plus I like the sorta "period style" it has..I am going to call them and order an extra flush tower just to have a spare (same with the Toto as nobody carries parts for these like HD or lowes). This pot uses a siphon jet flush with a pretty good wash down. I did turn the flush valve 180 degrees and turned the chrome button around so the buttons are the same config as the Toto. The costco unit has the full flush on the left but the valve will go in either way if that matters. The button looks the same as the ones on the Toto otherwise.
Just my 2 cents, and I am a homeowner, not a plumber..Still glad I put the Toto in the master as the "king's throne" but the costco unit will make dandy guest bathroom upgrades..