I have an older Fishman Syetem 1 on my 1999-2000 Larriveee D-02E.  It only has 3 band EQ sliders, thats it.  It sound pretty good for a basic system, of course, a K&K or other pickup would probably sound better, but the hole in the side is already there, so I'll live with it for my limited elec. needs.  I looked at the UST element, it is not flat and hard, like a Matrix, but is a braided metallic element.  Here's what Fishman tech support has to say about it:

That UST is called the Sonicore and it is only sold to our
manufacturers.  It is not sold in a consumer format.  Electronically, it
is compatible with the Matrix under saddle and you could replace the
Sonicore with a Matrix if it is broken, often with sonically superior
results.

(http://pic20.picturetrail.com/VOL1620/996154/12029192/270262115.jpg)

Since I already have a hole in the side of my D-02E, with any pickup upgrades, I'd probably want to install an attractive matching piece of sapele for a hole cover, and then go with a K&K.  I've also heard that some guys have used the larger Fishman Prefix onboard preamp, and hooked up a K&K pickup to it.  That would be cool.  I've always been surprised that K&K never came out with an onboard system that would allow an upgrade from a barn-door system.  I bet they are losing alot of sales by not having something for folks who want a barn-door upgrade. 

You could always use the barndoor hole as a soundport.

Quote from: bhika on August 07, 2007, 12:07:29 PM
You could always use the barndoor hole as a soundport.

Mount a LCD screen and you could scroll your words/chords off your guitar and not need sheet music!