I have had a really positive experience booking on VS. I did not have enough points in my account, they took my booking, and reserved my seats and did not charge the taxes until the points that I transfered from AMEX came thorugh.
I have called a couple of times in the past to check availability and they have always been helpful, and very good availability. I must admit though, an online interface would be preferable. They told me that the web site does not have that functionality yet, and they did not know when it would be completed. I really did not mind calling a couple of times to get the itinerary right....
..... much better than having a web site to check for flights and no availability!!