Bought this for the singer in my band, she's been trouble hearing herself while playing live and this caused some issues with her voice since she had to exert herself to be able to hear the vocals.
Bought this for her and after 2 minutes she was hooked.
The sound is great, the in-ear plugs filter out the sound really efficiently.
The only issue or "bad thing" about it is the display on the receiver is a bit scrambled during the first minutes of use (each time) at first I thought it was broken since it looked like an old digital watch that had been through a rough time, but we didn't have any choice but to use if since we had a gig the night after we got it, but after a few minutes the display was normal and you could read everything on it.
Maybe I just received a bad one :P
The rest of us in the band (4 more) are thinking about getting a few of these as well, while they're not the cheapest, they're definitely not the most expensive ones.
I recommend this to anyone wanting to start with in-ear.