I have been buying from General Circuits via their website PCBCart.com. The process is typically very fast for standard pcbs, once I have decided on the specs and quantity. I usually go through the quote process about 3 or 4 times to make these decisions, but once settled, entering the final specs takes a few seconds (most are default values in the selection boxes), then I place the order and it goes over to Paypal. Finishing the payment through paypal takes about 2 minutes I guess. Then file upload is done which is about a minute or so. Frankly, if it takes 3 minutes or 8 minutes makes no difference to me as I usually have invested many many hours of design and checking and so on, so when I make my order entries, I am very careful and go quite slowly, so if it takes overall 10 minutes, that's ok with me. As long as it is my thinking time and reading time causing the slowness. If it was the website causing slowness, I would get upset.
For non-standard pcbs (like unusual laminates and nonstandard dimensions) the order process can take 3 days via manual quote and question/answer via email (they are many hours different than my time zone).