It's a huge difference for me. I'd tried several styles of hiking poles in the past, but they were heavy & clunky enough that they just seemed to get in my way. It felt kinda like a poorly-fitting pack to me... strapped on & independent of my body and movement, not a natural part of it.
When I bought the LT4s it was revolutionary. I love them. I don't even really notice them in hand, but they go where I need them to go and give me all the support I need.
In short, lighter poles converted me from strongly anti-hiking poles to strongly PRO-poles.
In support of the lighter pole comments: I do a fair bit of distance canoe tripping. The weight of the paddle makes a huge difference in the way you're able to feel and perform, particularly toward the end of the day. There's a world of difference in a paddle that weighs just 6-8 oz less. The same thing applies to trekking poles in my experience.