Travel wise I thought the handling was just as good at the 140mm setting as it was at the 110 ( I had the 454 air u-turn pike), and most of the time I had it around 125mm for the trail and road (140 before I got the higher bars because low bars just didn't feel right). I played around a bit with the settings and could feel a difference between 110 and 140 but nothing that I thought was detrimental. Really going to 120 wouldn't have a huge mpact once you factor in the little bit of extra sag.
If you got the coil pike I believe the u-turn was adjustable from 95-140, so even more versatile, well that's what the '08 STP Pro (Aus) came with as stock, seemed geared towards 4x racing though.
Speakin of handling I did definitely notice that the Alias didn't feel quite right with the Tora on it at 130mm travel, it felt like anything more than 120mm wasn't good at all, just saying because I think I would have noticed if the same was the case with the STP.(nb Alias HA is 71, STP 69).
Now that I have changed the Tora from 120 back to 100 I think the steering is a little quicker and of course it feels that bit lower, but I haven't been for a decent ride since the change.
Funny enough I had mine set up as SS for a short while, but with 11/32 ratio it was too hard around here, too many hills to push up, and after one decent ride I found that for the first time I was getting sore knees, not a good thing, so now I'm running 1x9 as you can see. But on a road ride (15k's to town) the singlespeed took about the same amount of time as when it was geared.
I think there is an assumption that the STP can't take more than 100mm travel, probably because the US never got the STP Pro model like we did in Oz for '08...
In my opinion apart from the size (seat tube) it's not a great deal different from the concept of the Transition Vagrant, Banshee Scirocco etc