It depends entirely on your skill level. Skidoo made T-Mo to make less skilled riders ride better. And it worked. I rode my 13 XM a ton better than my 13 Pro. There is a point where it is a hinderance as skill levels advance. Locking it makes a difference in more than just sidehills. Yes, a locked T-Mo holds a technical sidehill 10 times better than unlocked. Less wash, more consistant. Where it makes a bigger difference for me is uphill climbs through trees. Take two trees that are 12 feet wider than skis. Try keeping it pinned with T-Mo and without. And not hit either one. THAT is what sold me on lockouts. Buddy on Pro went first, buddy on Cat second, I got stuck because I had to slow down to be sure that the sled wasn't going to dart into a tree. Both guys said they never lifted, I had to. Don't believe me, come to McCall for a rip and I will show you. And if anyone says that it is easier to tip up with a lockout, they don't know how to ride. T-Mo was designed to make it easier to tip up. Locked out it is harder to tip up, but holds it once it is there. Original poster, PM-ing you, as your question hasn't been really addressed.