Hi John,
I like my digitool. It is one of Darrel Boehler's original hand made
versions so it is relatively old. Can't remember when I got it from him.
Anyway, I like the quick visual aid it permits for the various functions
the ECU sees and monitors. It has come in handy several times over the
years. Specifically in my experience it warned me of potential and actual
failure  for the Oxygen sensor, temp sensor II, battery output and the
throttle position switch. So for me it was worth the expense, a useful
addition to my tool box, plus I admire the ingeniousness of Darrel to
think of inventing it. I made the mistake of ignoring its readout once.
The voltage for the Temp II was reading abnormal but the van seemed
unaffected til a week later when it became hard to start when cold. Sure
enough it was warning me the sensor was going bad. I didn't have a backup
so was forced to use a local FLAPS Chinese version. If I had not ignored
the digitool I would have ordered a sensor from one of the great vendors
we use on the List.
Rick Koller, Digitooler