As of this article, no one has released a native Insteon IR remote control.  However since all Insteon devices are backwards compatible with X10, there is a solution.

Assigning an X10 address to an Insteon device and using an IR543 X10 Infrared Commander Center allows a programmable IR remote control to control your Insteon device.

I use a Harmony 880 remote to control my home theater and my Insteon lights.

It turns out because of the way the Harmony remotes work, they are not best suited for X10 in some situations because they do not allow for macros. For example you can add x10 commands to your activity startup/shutdown but can not have it send an x10 command after pressing the pause button.

Also for anyone else interested in using the IR543 X10 Infrared Commander Center with a Harmony Remote (The 880 in my case), see this link: http://www.remotecentral.com/cgi-bin/mboard/rc-harmony/thread.cgi?3765 which includes a few tips and tricks.

I hope this is helpful.