It used to be useful to me back when my ISP had 28800 bps and 33600 bps capable modems in their pool, and I had a 33600 -- I learned to hear from the handshake

It used to be useful to me back when my ISP had 28800 bps and 33600 bps capable modems in their pool, and I had a 33600 -- I learned to hear from the handshake when I hit one of the slower modems and would then immediately hang up and try again until I got one of the fast ones ;)