The Listen Technologies has always been good: http://www.listentech.com/assistive-listening/listenrf/
I've never found a system (RF or IR) from the wireless mic companies that was as well thought out as assistive listening systems from companies that specialize in it.
We have generally used the Listen Technologies 3-channel units on our campus. They -- function.
I have never been a huge fan, mostly due to an aesthetic aversion to the overly-large and cheap plastic receiver beltpacks. In general I've found the sound quality with Listen single-over-the-ear earphones to be adequate, but not good. Still some static/white noise, but depending on venue, acceptable. It is a pain to order the Listen stuff. There are a million part numbers that make no sense by the time you get all of the rack-mounts, the right remote antenna and mount, signage package, etc. Grrrr!
In my latest project I have specified the Telex soundmate ST-300 and SR-50 receivers to try it out. More expensive than the Listen, but at least the part numbers make sense.
One of our vendors has spoken well of it, and says it sounds 'good', whatever that means in an ADA system. I believe it has more available channels, which may help in dialing in a quieter place in the spectrum.