(First post)
Several times. They're basically the cheapest way to get Canon (and Canon-related) gear from an authorized dealer.
CPW is just a broker that matches you to authorized Canon dealers who they have have pre-established deals with. This way the dealers can anonymously "advertise" a deal at less than MAP. Being that CPW isn't a dealer (in fact, they handle no goods nor transactions; they have no actual business relationships with Canon/Sigma/Tamron/etc.), they have no MAP agreements to abide by. Once you request the deal, CPW just basically hands you off to the authorized dealer, so all your business is actually done over-the-phone or by E-mail with the dealer. I'm sure CPW gets a bit of kickback (finder's fee?) for the business that's sent to the dealers' way.
The only thing that's limiting about CPW is that sometimes they won't have pre-established deals for items that aren't as popular, and so there is no "street-pricing" offer that you can take advantage of.
I don't know how Canon corporate really feels about this, but so far they don't seem to be cracking down. Perhaps the dealers just honoring their MAP agreements (regardless of how much the final transaction price is) is enough to keep the market from becoming a race to the bottom... and maybe that's all that matters.
There's another (new?) service called GreenToe that I haven't used yet, but it's supposed to work as a buyer's market. While there are buy-it-now prices, a buyer can make an offer on a desired good... and the dealers can decide whether they want to meet it outright, or privately counter-offer. You are obligated to buy the good if your offer is met, though... so don't offer on a whim.
