I own both the Xbox 360 and the PS3. If I do the mod to make the PS3 IR compatible, can I use the Harmony 550 remote to control both my PS3 and 360?? Thanks.

Your remote is able to control the XBox360, but your PS3 can not be controlled by it. The reason for this is that the PS3 is a bluetooth device, making it non-compatible with the Harmony Remote

Actually I think freshout1616 was talking about the mod to the PS3 (using a Radio Shack PS2 to USB adapter and the older PS2 remote control with IR receiver). This mod allows IR control over the PS3. It has a few limitations but does an excellent job of performing the basic functions for Blu-Ray playback.

As long as you have the remote setup for Play PS3 or Watch Blu-Ray - some specific activity that uses the PS3.

My theater has both the PS3 and Xbox 360 (with HD-DVD add-on) and my Harmony 880 and 1000 work perfectly with both devices.

Ok, sounds good. Thank you very much.