Honestly I purchased dozens of things there, and my experience was mostly positive.
Yes there is often a "verification" time (but like GamersGate) and some orders can be cancelled
The good thing: I don't have received defective keys on all my purchases and prices are sometimes better. They also have agreements with various publishers.
The big issue: the chaotic and not serious support (few answers by email or Discord, need to send multiple messages, bad tracking / escalation system: if an agent don't know, the request may be ignored, and the content of some answer is unprofessional)
For these reasons I think the experience could be described as "average" maybe "acceptable" (in comparison, I would have put GamersGate in very good, and Fanatical in overwhelming)
I think a good practice to improve GG Deals would be, in the future if the experience has been improved to reinstall Etail with an option to disable shops from user settings.