For me it's that I find they over hype their stuff. It seems like every batch with rare exception is a combination of:
a.) the last we'll ever see
b.) the nicest we've ever seen
And is priced as if both are true. About two years ago they were selling some Lee Enfields, and I got a nicer condition one than those in their videos for over $250 less. I have heard their customer service is not great.
I've also heard from many, many people that they scrub the reviews on their sites. So, if you get a rusty POS as many were saying their CZs were, that review gets removed, but a 3-5 star one will remain.
The "hand pick" is a scam, too, basically. They're just kind of sleazy in my opinion. It seems like every couple of months I see a "is this considered 'good' condition? Classic says it is and won't refund/exchange" thread. FWIW my SKS was obtained in a group buy from them (I didn't know they were the vendor) and it has been very good. The organizer of the group buy said they were a pain to deal with, though.
I'd say they're a step up from Mitchell's Mausers, but that isn't saying much.