I used to refuse to try mmorpgs because I tried several and though they all sucked. But I was pretty much forced to watch classmates play WoW's beta in College. I decided that it didn't share alot of the problems that made me hate the other ones so much so I decided to try it... Actually my family convinced me to get it believe it or not. still am enjoying it after almost 4 years now.
As for being a waste of time and money, it can be depending on how you enjoy these games. I personally do not feel it wastes either. For example it did not impede on my graduation at all, and it might have even helped me be more assertive around people (I used to be a total pushover, now I'm just an ordinary pushover >=P). But some people just can't manage playing an mmo and doing productive stuff at the same time. I think their problem (though I could be wrong) is that they push themselves into guilds,clans,organizations, whatever in game which demands a certain level of performance from the player to stay in. so they burn themselves out trying to be a model guild-mate for their entire mmo-career so to speak.
I'm in a casual guild (alot claim to be that but mine really is lol) that has a frustrating number of players who really quite...Suck. But the beauty is that I can decide not to log on for a month and I wont get demoted or removed or any of that nonsense. To this day I have some people look down on me (in-game I mean) about how I'm such a "slacker" in game in regards to farming gold, mats, whatever. I play when I want to pretty much, and that enough gives me enough gold to keep myself repaired, and have consumeables for "hard" content provided I don't waste it on easy stuff.
Generally if you want to aspire to being #1 on the pvp ladder or even close to that, or if you want to farm gold so much that you buy every possible vanity thing in the game, chances are you aren't playing the game for fun, and either you're a flat out addict, or you're doing it because you feel like you have to, which really ruins the point IMO.
Anyway, if you can play it in moderation, for fun, when you feel like it. It's really quite an economically smart thing to spend your money on. 20-bucks a month for entertainment is nothing. Nowdays a movie-theatre costs nearly that much, as does a single new movie purchase, or new music CD, etc.
I personally only log on WoW myself like twice a week or so after discovering Touhou >=P. I still respect it as a good game if played for fun and not necessity.