So since nobody has posted an opinion on the version of the legendary Sustainer humbucker, I glue myself!
You should know first and foremost we have here a micro rather unique, which is accompanied by its printed circuit board and its settings: a switch on / off (remember to turn it off, if the battery wears out, even unplugged guitar !) and a 2 position switch to toggle between normal mode and harmonic mode.
To get to the operating principle of the Sustainer itself: it is a microphone that is placed in the neck position and provides endless sustain (not just long, eh, really infinite stack up more!) on any note (in theory, I will come back because the practice is different) by generating a special magnetic field which keeps the vibration of the string in question. The normal mode extends the fundamental note and the harmonic mode shows a higher harmonic (which depends on the note), just like the feedback that occurs when playing hard with a tube amp.
So for me the good thing about this mic is simply what it is why does: it opens horizons not possible in terms of atmosphere, knowing that whatever your imagination may wish to add: prowess with a vibrato effects etc. ...
That said, it seems important to clarify things that are not specified and may disappoint (as was the case for me).
1) is a micro-level output very moderate, if you're addicted to solos neck pickup high gain, forget, mine is fitted with an EMG in acute sounds are different too, and there is a lag even more blatant in its clear, this combination can make dream is to be avoided (although the Fernandes is on some guitars ...).
2) its start through the microphone automatically switch permanently active acute, understand by this that whatever the position of your dial is the microphone that will work only acute and not another, and only while the sustainer is permanently active.
3) In fact, the sustainer does not act on all notes of the guitar, I can not seem to ring those of my little E string (that may depend on the drawing, but still, 10-46 ...), is widespread and generally no note after the 12th box, all the strings together, in harmonic mode.
However, I express a reservation on this shortcoming, it is possible that due to the fact that my guitar has 25 squares (the thing that is supposed to work for guitars or less than 24 boxes, issue of separation of the microphones ), so from this side, try it, it's the best thing to do (this applies to all the musical material as well).
4) The installation is really not convenient, unless you are very knowledgeable in electronics. Most stores refuse to mount, only a few luthiers agree to stick to it, think before you buy, remember to space for the stack, and of course that of the printed circuit board (the same size the microphone), knowing that both switches are welded, it can request a cavity in your e-stoned ...
IN BRIEF: The sustainer is a good mic, I insist on it, its sound is beautiful, it keeps its promises and open up new possibilities, but it has disadvantages that it is necessary to know before you get it: its output level is low, it is started automatically activates the microphone acute, it may not ringing all your notes, and it's boring to go
But if you do not play metal, it can do nicely ... Mine is mounted on a guitar luthier in body and neck (crossing) mahogany, the guitar is excellent, the EMG also the sustainer less ... So I do not play in micro acute, and by chance on a mahogany guitar EMG is less aggressive so it should be fine.
I use it for 3 months now, it's a good mic, although I was disappointed, I accommodates me, I do not intend to change it, but I will not go that choice ... I forgot the price, it's still expensive for what it is, but what do you, the competitors are so rare ... buy knowingly.
EDIT 11/08/2009: the guitar in question was given to repair a small problem of micro (with EMG this time, really ...), its parent took the opportunity to refine the settings, and In particular, ascended the Sustainer, which has completely solved the problem of output level that I had met, and in addition, now the notes of my first string sound (except in harmonic mode).
This is a great surprise, even if it does not remove some other inconveniences, for me the most detrimental was the lack of gain, so I go back to my grade 8.