Good company. Never had trouble whether buying or selling. Refunds are very customer-friendly though. If the customer wants a refund, he gets a refund. You have no choice. OTOH, that sort of policy inspires buyer confidence and leads to increased sales especially since most merchants promise a money-back guarantee. Fraud control is high. So credit cards that are legit will get declined from time to time. Again, this is good in many ways. Better to lose a sale now and then than to be hit by chargebacks due to stolen cards.
I was a vendor for a number of years and found two "problems":
1. It invited a hotbed of content thieves to steal my site content and my product content. If you're going to sell a product there, put plenty of controls in place before introducing your site or product to the public.
2. A number of the affiliates seem to be motivated by the commission percentage and ignore other important factors. IMO, this leads to some products being priced too high.
I've moved on and now use PayPal subscriptions instead of ClickBank. I'm well pleased.
On the affiliate side, I strongly suggest you purchase and use a product before promoting it if you care about your visitors and your reputation.