In fairness to the shops - it is true, some setups will mark the limbs badly and you (and probably I) would refuse to buy a set of limbs that looked second hand (at full price anyway!). However, the shops should equip themselves with the necessary's to allow you to shoot the limbs you want to try without damage.
I recently tried Samick Extremes and W&W Winex at Bowsports. It was a battle to do this but I had to do some pretty serious talking to convince them that I was a serious buyer - not just out for a play or someone who was going to go off and buy the limbs elsewhere/online/cheaper. I also padded up my riser with old tab leather to prove that I was serious
(I bought the Extremes BTW)
... so while I'd agree some of the shops are getting silly- if they won't let you try, don't shop there. You also need to blame the Saturday morning equipment warriors who go into local shops, waste a lot of staff time just so that they can say they have shot product X. Saddos
If you want it buy it
As for the Extremes well, I love the feel of them but I am finding them very unforgiving at my drawlength (~31.5" off a 70" bow) so I'm currently back on my aged G3s. My arrows are a little stiff and the G3s seem to wear that better. Can't comment on the Borders - haven't found a set of Borders I really liked since a set of 71" with 70" tiller I tried in 1992. (ie wood/glass)
YMMV good luck
Stretch