Hi all,
I just used K444404 in Austria for a 17 day reservation between May and June 2009. I was not questioned (or chastised) for using this code. Not sure if this was because it was okay to use or if the location was just so small (Linz, Austria) that they were not aware to flag this code. My next European rental will be out of Munich and I will try this code again in conjunction with my Avis Preferred Services card which should allow me to bypass the counter and go straight to my car (with applicable code in place). I'll have a back-up reservation with Sixt or Hertz just to be safe!