Have recently installed the Lyric in my all mahogany Martin 000.
Installation: As a complete non-expert, installation was simple and relatively non-invasive. No particular need for professional help. Other than drilling out the end-pin hole to 13mm (I used an electric router to get a really nice clean hole) there is no messing about with the guitar itself. No setting string balance, no repositioning the mike... just screw up the all-in-one end-pin socket/preamp, stick the mike onto the bridge plate using the double-sided foam tape provided; stick the volume/presence control to the inside of the sound-hole with the tape; stick the battery pack (I used the neck block) with the tape. I spent more time tidying up the cables than positioning any of the other components (there are stick on cable ties provided also).
Once installed it is of course (almost) invisible and has no impact on the acoustic performance at all.
Sound: After adjusting the presence control, the recorded sound is very natural and clear - far more so than any piezo I have ever heard. It sounds surprisingly similar to a studio mike set up, but less finger noise (but enough to sound 'real') and no need to keep still when playing. It is a mike, not a pick-up - so some external noise will be picked up on recordings.
Produces a really even spectrum with minimal EQ needed. Have yet to try out on stage, but have not been unable to induce feed-back playing at home. Four stars only because everything can be improved.
Not cheap - but very, very good!