I've had some bad experiences with them, But recently some very, very good ones.
The trouble for me is the price. At £110 for 30 mins, it's not really worth it for something that's so incredibly hit and miss.
If it's a help - Bella, Lara and Angelica are very good.
The one's I've seen that are disinterested and shite are Emily, Lisa and Lola - I walked on two of them because of their poor attitude.
Oh, I almost forgot; pay not attention to the on-site reviews. Most are so obviously written by either the girls themselves or the owner that it's bloody hilarious!