No problem. I think that is actually one of my favorite parts. One transmitter can do like 1000 receivers or something. I've seen a few movers and other fixtures coming out with built-in wireless receivers as well as at least one console that has a built in transmitter. Leprecon has a set of dimmers with built in w-dmx now too.
There is a bit of a trick to the w-dmx though. When you sync up the transmitter to multiple receivers, you have to release all the receivers, then tell the transmitter to sync. If you leave a receiver in sync then try to sync the others, I have had it lose any it was originally with. If you are doing seperate universes, your best bet is to plug up all the receivers and transmitters for one, sync them, then power those down and power up the second set and sync. Once paired, I haven't had any of them lose sync. It is rare that I have to re-sync mine usually just plug in and go. Just on larger shows if I sub out/from the other company we work with here. We own 2 transmitters and 3 receivers, other guys have like 2 transmitters and 6 receivers.
I think the big thing comes to how much you can trust the product as I know I was skeptical at first. My boss actually picked up the first set for us and I didn't even know when I would use it because I wasn't sure how it would work in my setups. I wouldn't say I use it every setup, but for my larger shows and certain venues we go into I will take a set.
-George