I've dealt with them for > 3 years without major issues. Their bizrate rating is accurate.
http://www.bizrate.com/ratings_guide/cust_reviews__mid--20881.html
Their religion makes them shut down by Friday 2pm so avoid orders by Friday afternoon or it won't ship until Monday.
They have increasing competition price wise from big catalog companies like Divers Direct, Scuba.com etc., and their business dealings is, in my opinion, a cut above these folks for inventory and promptness.
I would order 3 sizes of a product, not knowing which fit me, and return the other two without issue. My former buddy ordered an entire outfit, doubles through wet suit, and later returned the wet suit for an upgrade to a dry suit.
I've had similar snafus with other companies, usually when an item is not in stock but intransit from the manufacturer, expected 'any day now' so the customer in limbo.
What I would have done is had I not received the item on the first shot, cancel the order, or ask for something 'Mel' actually had in hand to ship.
I think the long poster did have a bad experience, but its not unique among mail order companies, including Amazon. Its not that the product did not ship, it did not ship as rapidly as expected or promised.
Now, if a product did not ship,or was lost in transit, that's a big problem. In the first case that's fraud and punishable by US law. Make sure you buy with a credit card that has purchase protection {Amex or MBNA gives that free with its card} and the item is insured, so if its lost, you needn't be left holding the bill for an item not received. I've so far not been affected by this problem.