A great mixer in it's own right, when co factoring price it's just unbelievable! We use the X18 both in studio and live. It has enabled us to have just one interface for:
1. Studio rehearsals, using the 6 buses for personal mixes through headphone amps (Behringer's own Personal Mixer solution - P-16M- still expensive for the 5 of us, but we'll get there!)
2. Studio recording, all channels simultaneously straight into the computer through USB
3. Live use, either only for in-ear mixes (we use a splitter to send signals to Front of House), or to make our own mix and send the final mix to FOH. Monitoring still with the 6 Buses through headphone amp, each musician using his smartphone to adjust his own bus/mix!
We've been using it for almost a year now, a dozen live situations, no problems whatsoever. Since we use no monitors on stage, the danger of feedback is almost zero (as long as gain levels on the mics are properly set), and the lack of physical sliders is therefore no issue. Small bar owners love the fact they can adjust the sound from a tablet being anywhere in the bar!
Highly recommended!!!