Not to be contrary, but...
Our boys (two labs) just came over from seattle via SFO on virgin, and I have to say that the experience I had was fantastic. My brother checked them in at SFO and had nothing but praise for the staff there. They always returned my calls, took my booking two and a half months in advance, and e-mailed and posted me information.
when we got to heathrow, a virgin rep came out to speak with us and explained the process, and gave us an update on the dogs, explained what that they travelled fine, etc, and really set our minds at ease. Then, he took our mobile number and said to go have some lunch and he'd phone us when the dogs were cleared through customs (which he did). All in all, a fantastic experience.
By the way, the woman who had brought her cat over on BA who was in the animal reception centre at the same time said, "Funny, I haven't heard from anyone from BA. I was just told by the ARC staff to sit here and wait, and that it could take up to four hours. I haven't heard anything since."
The other thing was that, because our dogs are big and there are two of them, it was going to cost about 60% more on BA--they would've required them on two separate airbills, both billed at the highest volumetric weight. I found virgin's pricing to be much more reasonable.
-Baylor