I suppose I should chime in, as one of the major proponents of them. I have been using them for a number of years now and they have stood the test of time for me in terms of reliability. I'll just highlight the main pros and cons.
PROS:
+ Smaller than all other standard N scale couplers*, so closer to scale size.
+ Compatible with MTL, Accumate, McHenry, and Kato N scale couplers. (But see the related con below.)
+ Single-piece shank with cast leaf springs, so no slinky effect.
+ The shank is very small in the vertical direction, so it is much easier to accommodate a lower ride height.
+ They never spontaneously uncouple, like some MTLs do when the slack runs in and out.
CONS:
− Only available direct from Lee English. (And who knows for how long.) Current price is ~$1.50/pr.
− There is no commercially available coupler pocket to house them. In the early days I teamed up with Ed Nadolski to develop etched brass pockets, but I have since switched over to custom-designed 3-d printed pocket, which have been GREAT. But none of these are easily available for purchase. (Most of my mature 3-d designs are available through TinkerCAD, for home printing.)
− Owing to the narrow shank, the shank axis is sometimes bent relative to the coupler body. This can cause some issues with perfect coupler height (I'm a stickler). These bent parts can usually be straightened with a bit of a twist.
− They don't "kiss" couple with MTLs very well, and sometimes require the 0-5-0 to mate them, but they do stay mated. (Sorry for the lewd metaphors.) They also don't kiss couple with themselves very well (takes a bit of force), but that's never been much of an issue for me.
-gfh
*I was recently loaned some cars with MTL Tru-Scale couplers that were modified by
@turbowhiz, to try out on my layout. My initial (and very limited) testing of these so far has been
very impressive. I hope to have something to report on later this summer, but I'm currently focussed on getting the layout back in shape for ops, so not sure when that will be.