The experience curve is adjusted to make it faster than ever to prepare for the newest challenges, and each level along the way will provide more meaningful increases in progress and power. All expansion zones are getting more flexible, too; they'll be able* to scale to you and your friends while you level to 50, so it's easy to try a zone you've never played.
One thing that has always been remarkable to me in World of Warcraft is how it brings players together from all sides of life to meet with common goals. I've been playing the game for fifteen years, and have played with gamers with all sorts of accessibility needs. I distinctly remember raiding Serpentshrine Cavern back in the day with an amputee friend Paladin who healed an entire raid of 25-players using a mouse equipped with dozens of buttons. He also competed at a high level in World of Warcraft Arena, as well as any able-bodied player I've seen.