We've owned two vehicles with the 7.3L PSD....one was a 2002 Ford Excursion and the other is our current 2000 Ford F350.
Both have been very reliable when it comes to towing. The cam position sensor was an issue for these engines and was recalled (a VERY cheap piece and a very simple fix too).
On our Excursion we did have to replace a single injector, but other than that it was fantastic for the 6 years we owned it. Our current F350 with the 7.3L needed to have a short in a wire fixed (was told by an International specialist this is a common occurence on the 7.3L trucks because the wire rubs on something and gradually wears the coating away) but that was it.
It's been very reliable in the 4 years we've owned it. Towing-wise we've towed a 9,000 lb. camper with both and always had plenty of power.
Yes they are loud, but I rather like that!! I would snatch it up in a heartbeat.