If a user issues `ifup ppp0' while the link is already up, the script saya
 ppp0 already up, initiating redial
and starts the advertised redial.  Subsequent `ifdown ppp0' commands fail
due to the absence of /var/run/pppwatch-ppp0.pid, and manual intervention
is required.

Redialing doesn't drop the line for long, so the first redial attempt gets
the `If you'd like to make a call, please hang up and try again' that the
local switch sends if you stay off-hook after the distant party hangs up.

Attempting to force a second redial manually (another `ifup ppp0' shortly
after the failed call attempt) seems to result in dueling chats: 
one chat sends a dial command, then the second sends a dial command that
aborts the first dial, causing someone to see `NO CARRIER' and retry ad
nauseam.