Mark, et. al.
I bought a Caroni 48" from Agri-Direct, it was $970 with curbside delivery and came with a slip clutch. It weighs in at just over 400lbs. It works great, although I really don't think I would want one that weighed any more than this. And getting the slip clutch adjusted was a pain, but now that it's done, it works very well.
Mine also "chatters" when raised while it is running, although it doesn't seem to matter what speed the PTO is turning. Somebody on another thread, I can't remember who, cautioned me on the noise. If the shaft hasn't been cut down far enough, it may be binding when raised. If it is, it could be doing damage to the tiller and the tractor PTO shaft (i.e. the transmission), even when the PTO isn't engaged. My understanding is that the lateral stress on the PTO shaft could destroy seals, etc. In my case, I verified that it wasn't the shaft binding, so I am assuming it is the U-joints making noise when the shaft is severely angled.
Kevin