I have ridden an SMP on 3 IM etc.
I was an "early adopter". It never felt really super comfy, but it had a way of making itself totally forgotten after 40km or so. The same saddle was great on my road bike and TT bike. Just slam it foward on the TT bike :)
I also found it to be the most "fit tolerant" in position and in pitch: more than once it got knocked back by a combination of potholes, nose ridding and lubricating sweat/water, and I'd be "these armrests are weird" and shift my hand position back... Only to find, in the paddock after the finish, that the saddle had slid all the way back... And it's a looong way back on an SMP.
Now, after 5 years, and having outlived my first two IM bikes, the foam is crushed and it needs replacement. But I bought my "Strike Pro" for about 90 euros (and I thought that was expensive) now an equivalent model retails for 180 euros. So SMP has priced themselves out of my possibilities.
Right now, I am experimenting with a Fisik Tri2, that works wonders on my road bike, and god is that thing pitch sensitive on the TT bike... And it does not have a hole to easily access the pitch Allen bolt from the top on my Felt DA...