Here's my other Trek which I got in November on CL. Happened to log on a minute after it was posted. They had many offers by the time I got there 40min later. It came to me as a complete bike, but I took the handlebars off so I could try out some other stem/bars on the rollers. A previous owner made a number of changes:

Helicomatic 27" wheels changed to 700C
Suntour Cyclone RD and downtube shifters changed to Shimano 600 SIS
normal stem changed to 70 mm
aero brake levers

It still has the half step plus granny 50/45/28.

I think I'm going to set it up for long riding and/or light touring. With rim brakes, one eyelet and one water bottle holder, I've got a couple of better choices for carrying heavier loads. I do very much like the geometry on this bike:

ST/TT: 63.5/60
wheelbase: 108
chainstay: 44.0
SA/HA: 73/73
fork offset: 55 mm
trail: 46 mm

I've got a 1985 model that I picked up about 8 years ago. I set it up as my all purpose bike and it has indeed been that - unpaved trail touring, year round commuting, errand running, hauling my kid around in a trailer all with minimal/cursory maintenance. It looks pretty beat now, but it has been a terrific performer. The 85 does have the canti's, though, and the longer chainstays (47?) of the 720.

The two components that have proven themselves beyond a doubt are the Schmidt dynohub and the Berthoud stainless fenders.

The Trek 720/620 are one of the all time great bikes imo. FWIW, my wife has a 1985 720 I set up for her.

Here is my 620 dropping my kid off at daycare:

I picked one up on ebay myself in December. It has already moved on to its next owner. This one was pretty original, including original Blackburn rack and bottle holder.