I believe this thread has already given you your answer, if you are basing your decision off of the opinions offered here. But I suppose it really depends on why you play the game.
If you play for the fun of playing, it seems that buying gold would circumvent a good deal of play time, which kind of defeats the purpose of playing, yes? If you play for the ego boost of being a digital death dealer extraordinaire, then sure! Why not? Your money will most likely go to a needy country where it will go to much better use than you just put it to! But if you play for reasons unknown to you, be very careful, because you are coming up against a lot of complicated psychological tricks.
MMO's are quite insidious, in my opinion. They are basically like online slot machines. You give them some money, and then, if you click your mouse enough, you get rewarded. But instead of having to shell out real money, like casinos, they give you fake money that you can only use in the game. They give you chips that you can't take out of the casino! Buying gold is basically the equivalent of buying more fake chips. Basically the equivalent of buying
Monopoly money with real money. If you really like Monopoly, then maybe it will be worth it to you?
Personally, I think it's crazy that Blizzard hasn't caught on and started selling gold itself! Imagine how much more they'd make if, in addition to your subscription fee, they could also sell you Itchy and Scratchy money to use in their digital fantasy world!