Updated drivers can make a difference, it seems.

Yesterday. Dial in to the intarwebz0r from home. Get a connection, as usual, of 49.5Kbps, which is what I usually get on this ostensibly 56.6Kbps modem. While I'm online, I have a look at the windows updates, see if there's anything non-critical I'm missing. There is an update for the Modem driver. Only a couple of kilobytes. I install it.

Today. Dial in to the intarwebz0r. Am rather surprised to see a connection speed of 115Kbps.

Either the driver is lying to me, or this update has been far more effective than I usually expect from Microsoft.