Many old school gamers seem to break out in hives at the thought of skills. I understand this perspective—somewhat—but I also strongly disagree with it. OSRians, or at least many of them, say that skill systems stifle creativity by creating a list of things you can do. I say skill systems encourage creativity, by giving GMs a framework whereby they can adjudicate whatever crazy action a character comes up with that isn't totally arbitrary. It also encourages creativity, because it gives you a options to customize your character, and even develop him during chargen (and beyond) giving him personality that you might not have thought of if you didn't have a skill system to play around with. OSRians might actually have an issue with this as well, if they're part of the "PCs are disposable game pieces and pawns, not characters" mentality, although honestly, I think that particularly mentality wasn't ever really that common, even back in the 70s and 80s. But whether it is or not, I'm not one of those disposable pawns playstyle kinda guys. I'm not a member of the "My Precious PC" club either, but I have always approached the game with more of an author's eye than a gamer's eye, and characters who are interesting, memorable, and maybe even unique, is an important aspect of the game to me.
One of the things that's really interesting about the m20 skill system (vs. say, the d20 skill system) is that not only is it very light (4-5 or so skills, depending on the specific m20 iteration, vs. what... 25-30 or so depending on the d20 iteration) meaning that it's not nearly as granular. This makes it not terribly unlike how we used to do it before skills were added to D&D, i.e. the good old-fashioned ability check. However, unlike with an ability check, your character can have a little bit more definition as a character than one without skills, in some ways. Instead of just have a DEX score that determines everything that has to do with your hand-eye coordination, speed, etc. you have a DEX score, but you can also combine it with the various skills to have a more robust portrait of what your character is; but without the detail, time spent, and straight-jacket feel that many players had with the d20 skill list.
Another is that since all skill checks are a combination of a skill and an attribute, you actually have a lot of flexibility to be creative. The simple act of climbing a wall, for example, isn't just a Climb check; it depends on how you do it. If you just haul yourself up the cliff, it's probably a STR + Physical; the most like a regular climb check. But what if you're trying to get up their faster than the Fighter? What if you're trying to be flashy? Why not a DEX + Physical for characters who are specifically attempting to do it that way? What about a character who spends a few moments studying the cliff first, searching for the best route and easiest hand and foot-holds, to create a detailed plan for how to get up the cliff before climbing it? A MND + Physical? Sure, why not.
And the best part of it is, the GM can simply adjudicate what to do based on how the player describes what he's doing. So players have the complete freedom and flexibility that many OSRians feel is missing from more modern versions of the game, while GMs actually have a more robust framework than, "uh... roll under your STR" or whatever to determine how it works out for the players. There may even be plenty of times when a player suggests actions by coming up with creative solutions that are specifically designed to maximize the abilities that they have. Whereas the fighter may simply move a fallen tree from the road by huffing and puffing and trusting in his strength to just pick it up to allow his carriage to pass, the wily, intelligent expert or sage might come up with a plan to use levers, pulleys, ropes, and leverage to do the same thing, bringing to bear his MND skill, which is probably better.
Rather than stifling creativity, it gives both players and GMs tools to encourage creativity.
But I always used the skill system in d20 the same way. I always decided what (as a player) I wanted to do first, and then expected the GM to tell me what skill applied (if it wasn't immediately obvious) and what DC made sense.
But a lot of this is "frame;" i.e., how do you approach the game has a lot to do with how you were brought into the game and the habits you set early on. I always played with the D&D vs. the AD&D paradigm, or as Tim Kask and some other guys suggest, my habits and approach is more old school even than AD&D. It's rulings, not rules, it's DIY, it's keep the game moving, etc. No matter what the system is actually built as, that's how I'm always going to run the game. I still don't completely understand why, if a GM wants that kind of game, he doesn't just run it that way. But I guess I do understand why having a system that actively supports and in fact demands that kind of game might be preferred to one built with some other assumptive play style.