Tyson:

I have X10 controlled lighting, automated through my Pronto. I use a IR to X10 controller purchased through smarthome.com (4040). You will need to get the Pronto CCF file from Michael Lynch, posted on prontoedit.com, called quick_x10.ccf. It has the necessary X10 IR commands for the Pronto for X10 on / off / bright / dim for all 16 devices of a housecode. Yes, it only supports one housecode. Note that I have found it is often necessary to send two X10 commands to get the device to respond, so save yourself some time -- when you are setting up the Pronto and you want to, say, turn on a light -- send the following:

Numeric pad device X
Numeric pad device X
Delay 0.1 seconds
Light on
Light on

I'm enjoying being able to control both IR devices and X10 devices through the Pronto. The possibilities are endless.

Have fun.