My LDS has a pool - like most, I suppose. They will let me compare any products in the pool. I find this very compelling although, at this point I only own my personal (fins/snorkle/mask/boots/gloves). I wouldn't take advantage of this service by, say, comparing two BCD's in the pool and then buying online; I want to have a good long term relationship with this shop [they are close to my house, offer all the training I want, very friendly, etc. etc.]
Also, they offer me a discount since I've taken my OW (and soon AOW) classes there. Now, even with these discounts, the prices are not even close to what you can find online.
I recently compaired lights that I'll need for my AOW class. Of course I can get a cheaper light package from the web. But when I went in (and told them that night diving doesn't really "attract" me, but I obviously need lights for the night dive in the class), they spent the time to explain that one particular primary light (priced around $40) is a "good" light, and if I decide to do heavy duty night dives and/or wreck penetration, I can THEN get a better light and use this one as my backup. Oh, and they will discount that $40 for me.
When I finally scape up the coin for a major investment (BCD, Reg set, Computer, etc...) - I'll probably do some online research, compare products in the pool, and politely ask if they can "do any better" price wise. I don't expect them to come down to web pricing, after all the customer service [read: personal time as well as the pool] is worth something. But even a little "rhythm" on their part will show some good faith from them that they value me and want me to come back.
I guess I've taken enough of your time - go on now and read a post from someone who knows what they are talking about.
...steve...