In reply to redline161:
Figure of 8s are quite slick, and also have a habit of kinking ropes. Most people don't use them these days as they are big and bulky compared to something like an ATC. Also, some walls don't allow them.
As for your original question - my VC Pro is very 'jammy' when top-roping on a tight rope, but is genearally ok when lead belaying. I thought they had fixed the problem with the VCProII, but clearly not. I have found the the reverso range from Petzl and the ATC range from Black Diamond all work perfectly.