Haven't used them that much but, on the occasions that we have, we've had no problem.
I can't remember what DVD it was that I ordered, but I placed the order in the morning and received the DVD 2 days later - a couple of days later, they took the money from my account and off we went.
The only slight problem was when one went missing in the post, but I rang them and they sorted it all out with the Mail - that only took a couple of days as well, and they sent a new copy of the film.
Keep up the good work, dvd.co.uk chaps