i used mailbox movies for a few months. Their service was good, and during postal strike times, they even refunded cash (2 weeks worth) to compensate the slow delivery times.
I didnt want all the latest titles, but the ones i did queue, i didnt get. I was after more TV stuff, like jeremy clarkson dvd's and kids films. Out of say 20 films i really wanted - i got around 15 of them (along with other titles to keep the kids happy)
Overall - their service was 8/10, selection 8/10, value for money 9/10
i had the 3 dvd service, and got around 15 dvd's a month (but i wasnt watching them on day of delivery)