With some of the modern technology out there, I'd have to say it's getting pretty darn close.
I just got my Sennheiser EW172G2 system the other day. I haven't had a whole lot of time to use it yet, but I will at practice on Sunday. So far though, I'm very impressed with it. For as long as I noodled with it, I didn't have any dropouts glitches or other anomolies. Tone and volume are right up there with the cable.
Frequency response and frequency agility were the two deciding factors in my choice of this system. I play bass and use my low B a LOT, so I needed something that would be able to handle it. I also live in an area with a lot of Military, police, TV, and other UHF transmissions going on, so I need freq agility. The G2 unit has 1440 channels and the ability to scan to find a clear channel.
We have three gigs next weekend, so that will be the real test of whether it works well for me.