Interesting site, "Visit our 149 International Coin Dealers." That's a lot of dealers, and while I do recognize some of them, there are many more I never heard of before.
I've purchased coins from four different dealers on Vcoins and never had a problem. I'm sure that it depends on the individual dealer, but I believe that they try to keep out any problem dealers that would ruin the sites reputation. I frequently check the site for new listings and wouldn't hesitate to order again.
There are some good prices on there too. I got a Panama 1904 50 Cent coin which they list as AU for US$110. Even if it's XF rather than AU, it's still US$40 below catalogue value. XF catalogues at US$150 and UNC catalogues at US$250