Here is something a did a while ago that might be of interest here. I recorded four samples as a comparison. One of them is running through a Monster cable. The other three are using the Line 6 G50 Relay with various cable simulation settings. I have written down in my notes which is which, but I haven't looked in a while, and I don't remember off hand.
I've been very happy with the Line 6 and have since upgraded to the G90 for the rackmount capability. However, it can conflict with Wifi, and you need to be careful when using it in an environment with Qmix. I have written down which channels should be used depending on which wifi channel is being used for the network. I'm very curious to se if this is easier to deal with using either the new Shure system or one of the new Line 6 units.
I have a Shure LX wireless from the mid 90's that I have used for a long time, and i was always happy with the performance of it. However, I did purchase a Shure SLX system not too long ago, and it was hands down the worst sounding wireless unit I have ever used. I immediately sold it and never even attempted to use it live. If anyone has questions on that, let me know. But Shure is a good company. I also use their wireless unit for IEM with great success. It sounds like their new digital wireless for guitar is a strong contender, especially compared to the Line 6 Relay, and I appreciate hearing some of the feedback from the people who have used it. It sounds like it has a lot of nice features, including the longer battery life.
Edit: I found my notes. The 4 samples are as follows:
1. Guitar through Line 6 G50 Relay with cable simulation set to 20 feet.
2. Guitar through Line 6 G50 Relay with cable simulation off.
3. Guitar through 20 ft Monster Cable.
4. Guitar through Line 6 G50 Relay with cable simulation set to 10 feet.
Other notes: When I said there were issues with the wifi when using the Line 6 Relay and Qmix at the same time, there was never an issue with the guitar wireless. That always worked flawlessly. The issue was the Qmix would not stay connected to the host. This problem is solved if you use the correct channel.
Also, I contacted Shure when I had issues with the SLX system. Their recommendation based on the issues I was having was to use one of their digital systems. The impression I get from both Shure and other reviews I've read, the Shure digital systems are much better than the current analog, at least under the $1000 price range.
I hope this helps.