I'm using the 2 pin Ba-X variant and I REALLY like it.
I got mine from Cosmic to fit my Cosmic CIEM'S.
I have two pairs of CIEM'S from Cosmic and the socket of one of my 'better' pair is too loose due to (I think) the original cable having a slightly oversize pin stretching out the socket on the left monitor.
The right fits fine, nice and snug, but the left almost falls out by itself.
Phil at Cosmic has offered a couple of different solutions and in the meantime I've been trying the cable in my other Cosmic CIEM'S (single driver 'Pure' model) as they fit these perfectly.
I haven't had any mishaps which would test the strength of the cable, and I'm still getting over the urge to 'baby' the super skinny cable, but I'm getting used to it.
Comfort is unequalled in my experience.
I agree with others who have said it's almost like wearing the monitors without the cables, with the advantage of actually being able to hear music!
I have a pair of Sony MH1-C's which have a much bigger flat cable (modded to overcome the annoying 'j' design) which is also pretty comfortable worn over the ear, so I don't necessarily ascribe the comfort to the 'dental floss' thickness of the linum cable.
My personal view is that the softness or flexibility of a cable is the defining factor deciding the comfort of an over ear cable.
However, I find the flexibility of the BA-X VERY comfortable.
As far as sound goes (mostly cable sceptic here btw) I'm probably imagining this but I find that the bass seems very slightly boosted, and mids a little more recessed than before (tiny amount).
This is probably just due to a comment I read somewhere that the BA-X slightly promotes the 'V'sound sig'.
I must admit that this is the opposite of what I'd want with my best CIEM'S as they're reshelled TF10's which are already a tiny bit too 'V' shaped IMO.
The effect is so minor though that I'm entirely willing to put it down to placebo, or buyers remorse (I wouldn't normally spend this much on a cable, 'cause I'm tight), but any remorse re' this purchase is overcome by the definite positive aspects of this design.
One clearly obvious sonic advantage this cable had over every other cable I've used is that (misnomer alert!) microphonics are greatly reduced, almost to the point of elimination.
Apparently Cosmic are ditching the 2 pin plug entirely, in favour of the new Linum plug/socket.
I think this is a great move as if the published specifications of the new combo' are accurate they clearly outperform the 2 pin by a huge margin in this application.
Although it might disable the Unique Selling Point of the linum cable, for some people a thicker more robust version might be more attractive.
The published pull strength is very impressive for a cable this thickness though, so a thicker version is probably physically redundant, but it might increase 'perceived value' and confidence in the longevity of the product.
To summarise; Durability pending more use, I'd definitely recommend this cable.