Yes, I have bought several things from CDNN and they are good to go...for a discount seller. High volume, low price gun dealers such as CDNN, Bud's, etc. put most of their customer service resources on the sales side. If you encounter a problem after the sale, do not expect a speedy & customer focused resolution.
Bought several guns- flat shipping charge, only bad thing is that their catalog is printed every quarter so if you wait until the last month of the quarter they are usually out of a lot of items.
$9.99 shipping on ammo regardless of the amount and $9.99 shipping on accesories regardles of amount as well but both charges cant be combined, meaning if you buy ammo and accesories you will have to pay 2 shipping charges.
I bought one from them as well, an HK, went through Seth per recommendations. Great price (20% lower than anyone else) the gun was at a local FFL in 3 days, was great.