Going for IEM resulted in a drastic improvement with respect to how differently I sing alone vs with a full band - it used to be that loud volume on stage and limited possibilities to hear myself gave me trouble singing even songs I could sing well without the noise, but IEM fixes this to a very, very large extent.
Ok, this device certainly doesn't provide the pristine audio quality of a fat cable or a high-end wireless system. Guess what? Often it doesn't matter. As it is (most likely) for sound that's not going to the audience, one can reasonably tolerate a bit of interference, while enjoying being wire-free and not having to rely on stage monitors, and having the satisfaction of having paid almost nothing for this freedom.
The included earphones are not good, but I never planned to use them anyway. Just assume that the money you're spending on the t.bone IEM75 system only goes towards the transmitter and receiver (still extremely cheap), add any decent earphones, and you'll be fine.