I haven't received my USBUIRT yet, but I have a lot of experience with infrared distribution, as that is how I currently handle distributing/controlling my media from a single location to all rooms of the house.
You have several options for controlling multiple components. The first and easiest would be to just put the USBUIRT in a location where the blasters could hit all your components. This would be very easy in a media closet or small rooms, and might even work well in larger rooms if the blaster is strong enough.
The next option would be to use the external port, which can power a dual-emitter. These are the little "bugs" that you stick directly onto the IR window on your devices. Now if you need more than 2, you can plug that port into a connecting block like this: http://www.hometech.com/infrared/blocks.html#XA-79144
That's a big model that is amplified and has 10 ports, and you can chain them together for an unlimited number of devices. They also make smaller 4 and 6 port models.
Another option that won't be as common, is a hybrid solution, which is exactly what I plan to do. Since I already have my infrared distribution system setup, and all of my devices are already "bugged" with emitters, I'll simply point the USBUIRT at one of my existing IR recievers.
If you want to learn more about infrared distribution and all of the cool things you can do with it, a good place to look is the Xantech catalog - http://www.hometech.com/pdf/xa-x2006.pdf
. They have several different scenarios and examples in there that show how their components can be used. Not all of them will be applicable to LMCE, but you might think of other ways to apply them to complement your setup. And if you get into this stuff, definitely stick with the Xantech equipment. I've been doing this as a hobby for 10 years, and I've never had a piece of Xantech equipment fail.