Im using a Shure GLX-D 2.4ghz digital wireless for my guitar and it's been flawless. Love the spare battery charger/storage slot that the battery slips into on the receiver too. Body pack is very robust also. Overall a very well thought out design.
The only issue I had was some occasional interference (guitar signal would click) that was found to be caused by our digital desks wifi router. We have everything crammed into one rack so the Shure guitar reciever and the router are literally only a few inches apart. The most robust solution was to swap out the router with a cheap dual band model (2.4ghz and 5ghz) and simply only enable its 5ghz band. No chance of interference that way and everything has been perfect since.