I haven't actually played much this expansion. But it's never too late per se. Now is actually a good time as you will have lots of time to level up, explore and figure things out before the next expansion.
Each expansion is a sort of reset for everyone. The gear in the new content is more powerful, the level cap is increased and so are the professions. Trying to catch up at the end of an expansion cycle can be a lot more daunting.
WoW can eat up a lot of your time. I have somewhere on the order of 500 days played, I'm sure others have a lot more as I was inactive off and on. I have been playing since December of 2004 though, so it's been pretty well spread out.
I'd say it's a fun game. The world itself is large, fleshed out and full of lore tidbits. The quests can get a bit repetitive, however they have significantly improved many of the old quests and the overall flow of the game.
You can always do the free trial as well, which I think lets you play up to level 20. That gets your feet wet at least, without any real investment.