Well I've been with some of the major dvd rental firms:
BlockBuster, ScreenSelect (b4 merger), LoveFilm (after merger) & Amazon.
The best by far was Amazon.
Very quick turn around, they never missed one DVD that I wanted and 90% of the time it was the DVD that was at the top of the list that I got through the post. The rental service was very cheap (3 disc service), and customer service was and still is excellent.
BlockBuster comes in 2nd, as they're customer service was good, turn around of dvd's was ok, they did miss a few dvd's that were in my top 5, but only 70% of the time.
LoveFilm, sorry to say is just dreadful. Before they merged with ScreenSelect, SS was great. Their service was better than BlockBusters, but when the merger happened, I stayed with them for 3 - 4 months, but then threw in the towel. This was because LoveFilm's Customer support was just awful. It was like talking to primary school children on the phone and by email as they never understood what you were saying, well except when I wanted to cancel the subscription lol. But the DVD service was - no worRAB can describe it. the odd one or 2 per month on Unlimited service. They're excuse was they must of lost in the post in your area, because of this reason you will be charged for them going missing as no one else is having trouble.
Did that get a huge complaint from me as I told them I had signed up to Amazon at the same time and theirs were getting through no problem and it must be either they weren't actually sending them out or else someone at they're company was stealing them.
They never did tell me what was happening, but my subscription was cancelled. But they continued to send me "special offers" by post and email trying to get me back. But seems like they've won in another way with purchasing Amazon.
But seeing as Amazon are now going to be a major shareholder in LoveFilm, I just hope they are going to listen to their customers, or their old customers.