[quote name='yukine']Is Halo 3's multiplayer really worth the cost of admission? I have no desire to play the single player, at least not anytime soon.
I ask because there's a

load of games coming out this month and the following month, and I'm already a bit low on cash. I need to choose my games wisely.[/quote]
I'll give you an honest answer, Im not a Bungie apologist, or a Halo fanboy. Im just a fan of online fps games.
Halo 3 has 11 multiplayer maps. And only some of those can be played with certain game types. So if you love a certain mode, like cap the flag, or whatever, there may be as few as 3 maps to play that mode on. And out of the 11 maps, some of them really suck imho. Although some of them are great as well. After playing everyday since the game came out, I can say that they need more maps asap.
The matchmaking mode (picking online matches) is completely broken. Unless your playing with friends, you can NOT pick the map you want, or the game type. Its random. You may get deathmatch, you may get oddball, or Juggernaught (all against one). You basically have no choice in the matter. Also, you better learn to LOVE hammer or sword only games, as they come up plenty. Same with Shotgun & sniper rifle games.
Imho, its inexcusable for Bungie not to allow you to pick the map or gamemode you want. I can see it being random for ranked matches, but for social play, you need to be able to pick what you want.
This omission makes the map editor mode, called 'Forge' basically useless, cos theres no way to put your custom games out there and get people to play them.
Now the actual multiplayer action is GREAT! Its awesome fun, and even if you dont want to play thru the story, the multiplay is worth the $60. But the longterm value is comprimised by Bungies HORRIBLE design choices in not letting you pick what you want to play.
For me, they turned a game I would have played online for years, into something that Im already getting tired of, due to me not being able to play what I want, when i want.
If you dont mind playing what Bungie wants you to play, you'll have a great time. If you want to play what you want, the game will grow tiresome.
I still think its worth the money, but once COD4 comes out, Halo 3 is going on the shelf to stay unless they release a patch that corrects their horrible, horrible matchmaking.