Feature:
The ability to feed the transmitter two channels off the sound board allows you to balance the receiver between one channel or the other. So for my mix I have vocals on one channel and the band on the other. Using the balance control on the body pack, I get both channels through both ear buds but can adjust the loudness of each to my preference. I have the vocals turned up slightly higher than the rest of the band. The ability to adjust the levels by myself rather than our sound guy gives me a custom mix. I always leave the limiter on to avoid exceeding safe listening levels. The body psck includes a jack to attach an ambient mic so that you can mix in audience sounds but I haven't found a need for this.

Quality:
So far the unit has held up well. I've dropped the body pack a couple of times but it has sustained no damage.

Desirability:
Having made the transition from floor monitors to in-ear monitors, I can't imagine ever going back.

Sound:
The included ear buds are fine for general use but I've replaced them with Shure SCL5. OTherwise the sound quality including frequency range are very good. The optional limiter prevents the unit for exceeding safe listening levels. I've experienced no interference or dropouts at a distance of about 50 feet between the transmitter and body pack.

Ease of Use:
Pretty simple really. Plug in any ear buds and adjust the overall volume and balance between the two channels. I replace the batteries before every show just to ensure that they don't run out during a performance. I do the same thing with my wireless guitar transmitter and mics.

Support:
I haven't had to contact the company for support.

Overall:
I would likely replace the M2 with another M2 as it meets my needs at a reasonable price. The only reason I would consider another model is if I ran into some contention with wireless frequencies but so far it has worked flawlessly everywhere I've used it.

Feature:
The chord is so short that you can't lean forward, with the unit in your backpocket, or the earphones will be pulled out of your ears.

Value:
NO buy the shure unit, psm200

Sound:
If you play in anything more than a coffee shop then this product just isn't loud enough.

Support:
I called with problems in the first system they sent me (I sent it back because there was no volume at all) and the CS person was rude to me and told me that I obviously didn't know what I was doing. I do know what I am doing and there was no sound at all.