It's a simple guideline for structuring a non-combat scene, meant to be a help in deciding when to begin rolling and when to end. It is also a prompt to help communicate to the players 'be creative, come up with unusual action and ideas to put your strongest skills into use'. I myself found it extremely useful.
Ultimately it would depend on your DMing style, I guess. If you are experienced as a DM, if you have no trouble with identifying interesting conflicts of skill, setting a good pace and knowing when to move on so the game doesn't drag and people get bored, if your players are proactive enough that they have no problems knowing where to go and what to do and all agree on what to do as a team in a timely manner, then the system is going to seem of little value, but then again a DM with skills and a group like that, doesn't really need a skills challenge system, they can do just fine with 'what do you do?' and adlibbing.
Myself and my players were very much NOT one of these groups; we have always had major problems with players not knowing what to do when there wasn't a fight going on, or fixating on a scene and becoming convinced that there's some secret there when there wasn't any, I had problems with having them roll and roll for trivial stuff that had no importance and made no difference, we would often get 'what now?' moments and boredom, etc, etc, etc.
Since I adopted the 4e skill-list and skill-challenge system (or my own interpretation of it) in our 3.5 games, the difference has been dramatic. We have none of our old problems, and we have way too much fun on non-combats... so much so that I've recently been toying with the idea of having entirely non-combat game sessions every now and again
To illustrate, here is one encounter we've played through where the rolls went particularly well: The characters are travelling through a forest and come upon a large tree. There's a dead, naked man hanged on the tree. I announce a challenge with a general skill DC of 18 (I don't say how long the challenge is, but it's 6/4).
The rogue decides to walk up to the corpse and inspect it with Perception. He wins the roll and notices that theres a dry red line of blood going from the corpses throat to his groin, like he was sliced completely open then put back together. The wizard uses his Insight to try to understand what this means, and fails. The Ranger uses his Athletics to climb up the tree without disturbing the corpse, and wagers a Hard roll on it. We wins the hard roll and I offer him a second success with another skill, he chooses Nature to inspect the tree itself and I describe the tree's dryad being pleased with him and making herself visible to the party from the branches of the tree. Meanwhile, there's a discussion amongst the players which results in the Samurai trying his History skill to see if he has any knowledge of any historic battles where people were hung from trees after being sliced in half and re-closed and why someone would do something like that; he wins the roll and remembers tales of honorless dogs of war who would hide balloons of poison gas inside corpses and make traps out of them which would trigger on touch.
We cycle back to the rogue, who tries to climb the tree as well and fails. This makes 2 fails, but they need 4 to fail the challenge and set off the trap, so I describe him falling and just narrowly avoiding hitting the corpse, and it swaying dangerously and the top of the cut splitting just a little bit. Everyone gulps. The wizard tries diplomacy on the dryad and asks what she knows of this corpse and why it's there. He wins, and dryad tells him she doesn't know why the corpse is, but that she's sure a black satyr (enemy of hers) has set it up there while she slept in hopes of someone triggering it and killing her tree. The ranger tries a Hard thievery check to secure the corpse and cut the rope, which he wins.
The party now has the 6 wins, so they've won the challenge, but I say nothing and I let it play out. The Samurai rolls athletics to catch the corpse gently and makes it (but it wouldn't have burst anyways since the challenge was won), then the rogue describes burying it so that it won't hurt anything else, which I tell him he doesn't need to roll, they have won the challenge, they clap and cheer a little bit, and the dryad thanks them and gives them some advice and the traditional wooden magic item that dryads always give as rewards
All this happens in the space of 20 minutes, with everybody on the edge of their seats and engaged in what's going on, noone wandering off to do something else, no boredom, no 'huh?' moments, no 'dead air', and ends up really satisfying and fun for them and me. Now, is doing this possible without any challenge system? Sure why, not. If you can do it, that's great. Would it have been possible for us to pull off this well without the system? I know myself and my players well enough to say not in a million years So that's why the system is great for me. Sorry for the too-long post, btw, I'm just a bit excited about it.
