I think the more logical question would have been:
Anyone NOT using old soda kegs?
I think everyone that kegs has had one. I just got two more in. I have 2 Firestones and 2 Cornies. All 4 had the O rings replaced and I just ordered a small kit of crap for when something goes down. Im a newb to kegging but the process has been simple. One "IN" nozzle on a corny was absolutely APED on, other than that it was pretty basic.
just check the price against new unused cornys. ive seen some sites selling new ones for about the same price people are asking for referbished ones. i have been looking at kegging and in my area new just seems like a better deal the long run.