I have not tried much of the summoning skills but I have extensively used poly (I play solo not with companions).
Wings: Honestly I find this to be the least useful of all of the skills. I am not entirely sure why everyone is making a fuss about it. I hardly used it actually. I used the "movement" abilities from the other trees far more often. I pretty much only used Wings for running away.
Chameleon: Extremely good skill. Hopefully in the main game they give the rogue tree an earlier invis and chameleon comes later in poly.
Chicken: decent spell, fun to mess around with. I honestly didn't find it that overpowered.
Tentacle: Very solid awesome skill. Loved it. Made less use of it later on.
Skin Graph: This skill is ridiculous. At first glance I thought it was garbage but after messing around with it is has the potential to be completely broken. As demonstrated:
Elf rogue: first turn ---> Flesh sacrifice, Adrenaline, Burn My Eyes, Haste --->Vault(backlash), Sawtooth Knife, Throwing Knife(at this point whoever you targeted is pretty much insta gibbed or really close to it)--->Chameleon
Turn two: wait.
Turn 3: Skin Graph----> repeat turn 1 minus Burn My eyes---->Chameleon---> Walk in Shadows out and run away at mock jesus speed.
wait for cooldowns and repeat until everyone is eating carpet.
