After messing around with LPGs and guitar a bit more (with more focus), I don't know of the end result is different enough from the OTA style, vactrol based envelope filters like the Mutron or Maxon.
With the Mutron and Maxon, you have the fingers and string decay doing the VCA part. With the MASF, you have the envelope follower doing the same thing but usually it will be close enough to natural decay. The resonance and cutoff decay is similar enough between the two styles (and probably varies depending on vactrol or led/ldr setup).
I think the only way that a traditional LPG would be worth the effort as a guitar envelope filter style effect would be to have an edge sharpener with a comparator triggering an AR envelope (like a function generator) with times shorter than the sustain for guitar. CV control over the rise/fall times would give some dynamic variety. I think an addition like the damp control or the strike from make noise would be good because it would either give you more variety with automated CV or the ability to just run a trigger in (like an SQ-1). Klang off a RYO Aperture would work too.
Pairing the LPG with a pedal setup like the Malekko Sneak Attack would be pretty good though I think it would need additional CV control.
The emulations in the Roland Aria were just too noisy without converting to modular levels (just use an LPG at that point). The setup ended up just sounding like a really noisy and terrible maxon.
With an EXP pedal, I think, if one had the discipline, some nice LPG sweeps could be had but I don't know if feet can move fast enough to really get that ping/strike sound with quick attack and quick decay (the kind of bongo sound).
One great use for the LPG in a guitar context is sidechaining. Take the CV out of an envelope filter or run a comparator like the Bastl klik in parallel to control another signal like a radio or samples. It could also be used like a resonant noise gate for a noisy parallel signal or gated reverbs/short delays. It could really shine in a parallel path style pedal board or with some stereo stuff.
As for the MASF Tortam, the one I have is too quick on the response to really use just with a trigger generator. It's pretty barebones and needs some planning to really work. There really has to be some kind of envelope generator, LFO, or some CV around for it to really be worth it and usually pedals with CV envelope followers are usually either synth or filter pedals that kind of make the Tortam redundant. It's excellent at integrating in drone machines into a modular environment or sidechaining off another signal though.
LPGs would be useful to tame a noisy carrier signal on a ringmod when used with an envelope follower and add little variety to the setup too. (Had to mention ring mod or it wouldn't be me). They do make fun little tremolos when used with an LFO. I kind of think of LPGs as utilities instead of that magic tone or something providing that missing "mojo". It's a solid building block.
I think there is room in guitar land for a robust LPG gate setup that is more robust out of the box.
Here are some high hats triggering an envelope follower that opens the low pass gate (MASF Tortam). The transistor radio is running through the Tortam to the delay.
[youtube]
http://www.youtube.com/watch?v=8XC1MQ0-vc8[/youtube]
http://www.youtube.com/watch?v=8XC1MQ0-vc8
Interested. 
thanks for the replies 
Def interested in Tortam, but playing around with/re-housing a cheap euro lpg is sure to be a rewarding and educational experience :zippy: As usual, so much food for thought in your posts.... 
A low pass filter w/ a 20ms envelope attack time seems very promising. Also, hadn't thought about the downwards sweep. 
