I've got the 2009 Quad in Red and I ride it at the track with no worries...I think its great.
Like the guys said earlier, the geometry is different on the new ones, which I prefer as I don't break my knees off when I ride it!
I dont have any issues with it being flexy (but I'm not all that heavy so it might be different for others). I wasnt that fussed with the red and gold but I've got used to it now and I quite like it.
The old ones were made from Reynolds 501 were'nt they? whereas the new ones are Chr-mo.. no probs either way.
You need to ask what you want it for as I had an original Ripper and DB Silver Streak which I didnt enjoy riding as they felt too small for me, I got a new Ripper with a longer top tube (same as 2009 Quad I think) and it was much better...however, the old ones look great...so what do you want it to do? Ride or be looked at?
Either way, you will still be buying a nice bike.