I think this one was listed for the v6 an diesel.
Any how, first impressiosn - well worth it.
its hard to define, but basicaly thr car feels a whole lot more solid, like a better built/quality car, it feels firmer (not the ride just the whole car) less wollowy, more taught gives the impression of being a better quality car, so the 'feel' is realy nice like a new car really
It corners much much flatter, very noticeable, is more contolled and has a more 'considered' feeling to bumpy b road bends, bumps in general, much better feel, far more solid and 'grown up' i.e. better handling on non perfect surface, and flatter on all
initial Turn in is slightly improved, but at the expense of later understeer as there is a little bit more understeer when pushing it, but really hardley noticeable at all, and a GTA rear AR bar would cure that for sure though probably isn't at all necessary on the TS as is hardley anything(i expect in a v6 or diesel, the combo of front strut brace and rear GTA ar bar would really sort out the understeer nicely on the heavey engines 156's with a strut brace).
braking esp on bumpy roads is more surefooted, and front dives less.
Overall, the feel of th car is much improved, it really is noticeable, but that is because the 156 is relatively flexible, so on the new 159 (stiffest chassi in class) i expect the benefit to be minimal/not noticeable.
For a 156 TS I saw its a must
For a 156 JTD or V6, its a must but you will have to add a GTA rear AR bar, or it might be understeer hell, with lots of parking in hedges!
If you in any doubts, and can get one for about 50-60 notes, then don't wait, JFDI
overall, small improvements, but very effective and some very noticeable