The game being based on d20 at all kept me away from it for years. I got into Conan finally because I love the stories and the universe. I missed most of the 90's and the 3E explosion, preferring to play other, less crunchy games, like D6 Star Wars, Classic and Mega Traveller, The James Bond RPG and Top Secret/SI, FASA's Star Trek, among others.
But, the Conan RPG was written so well. When the Second Edition came out, I had to give it a try, and I just fell in love. I had played 3E D&D before, but the Conan game was different. In fact, I see many players come from 3E D&D to the Conan RPG and think of it as just another clone--just another cover on the same set of rules. It's not immediately obvious, but the Conan RPG, albeit quite similar with many rules, is a very different game. You can't play it like you can D&D.
For example, in D&D, I've seen many players rush from one fight to another. There's a Giant Spider, let's kill it. There's a Wyvern! Pull out the bows! If you use that mentality with Conan, you'll find the game to be extremely deadly. Although you're playing with very similar rules to what you would use in a 3.0 or 3.5 D&D game, those subtle differences that I mention can make for a rude awakening. For one thing, the Conan game is much grittier. It's meant to be a low level game world. Character advancement is left to the GM, but it should be slow. In my game, characters typically have to kill 10 foes of equal level in order to advance a level.
While the characters are kept lower level, the weapon damage is higher in Conan. A Short Sword does 1d8 damage. A standard Crossbow does 2d6. A Broadsword does 1d10. A Bossonian Longbow (roughly equivalent to an English Longbow) does 1d12. And the two-handed Greatsword does a whopping 1d10 + 1d8 damage.
Add to this that Massive Damage is triggered at a mere 20 points of damage (if 20+ of damage is done by a single attack, then the character must save or die, regardless of hit points--this is to account for all the heads and body parts that go flying in Conan stories) and the fact that magical healing is virtually non-existent in the game universe (no handy potions of healing, and no Healing spells), and, all of a sudden, the game that you thought was a 3.5 D&D clone in a new wrapper doesn't seem to play like a 3.5 game.
Plus, the Hyborian Age is not a game world of Orcs and Goblins. Typically, what you are fighting is a human, just like you. A single human foe can be so much more deadly then a group of Hobgoblins or Bugbears. Sure, there are monsters in the Conan game, but when you see them, they are typically stronger than what you might come across in a D&D game (where as the D&D game will throw at you several fairly easy encounters, the Conan game will give you fewer encounters with much stronger enemies).
In combat, the Conan player has to think strategically and tactically. Avoiding fights is usually a priority. Instead of just rushing into fight, from one fight to the next, it pays for players to study the landscape. Set up ambushes. Use surprise. Shove foes into fire pits and off cliff tops instead of engage them in melee. Parley is a favored tactic--maybe the encounter can be overcome by a simple trade....
As for the d20 mechanics....
IMO, the designers of the Conan RPG did a brilliant job taking the system and molding it for a gritty Hyborian Age atmosphere. Yes, there is a HUGE learning curve, especially if you've never played a d20 game (like me). Even if you have, as I mention above, the game is subtly different enough from D&D that many players will think they know the game when they really don't.
At first, the Combat Maneuvers seem like a lot to learn. And, on some level, it is. It's akin to learning a lot of spells for mages. But, soon, you pick and choose what you learn (you don't learn 9th level spells if you are a 1st level character--just focus on what you can use), use it in a game until you learn it.
A typical Conan combat might start out with two foes feeling each other out. Circling. Not yet in actual combat. One warrior stares at his opposition. He hefts his shield, grins, and slaps his sword blade across his shield.
Then, they move in to strike at each other. Initiative is rolled. The character with initiative takes advantage of the fact that he is quicker, catching his foe flatfooted. On the foe's turn, should he be still standing, he tries a feint--if successful, he too will have an advantage similar to catching his opponent flatfooted.
Next round, one of them uses Demoralize Other (a use of the Intimidate skill) in order to gain advantage. The other shoves off from a wall, coming at his opponent quickly, using Use The Battlefield to gain a bonus to hit.
And so on....
