From time to time, I see folks throw the terms 'fun' and 'competitive' around like they're mutually exclusive concepts, but 'competitive' and 'win at all costs' seem to be the same thing. Usually, WAAC is leveled by folks who thing fun =/= competitive, and it's used as a mark of shame. (Just ask the Arbiter what branding and the mark of shame are like. Go on.)
I think that distinction of 'Fun' or 'Competitive' is a false divide. I am going to go ahead and cite some influence from Sirlin, who I highly recommend as reading. I'm also going to say I think there's room in this hobby for playing for fun, and having fun competing, but not WAAC. I think it gets down to the people.
Defining Some Terms
I intend to use 'playing for fun', 'competitive' and 'Win At All Costs' (WAAC), but I'm going to offer some alternative definitions.
Common use of 'Playing for fun'
I'm under the impression that most people who 'play for fun' take stuff they thing looks neat, or otherwise pick armies that suit your fancy. In a sense, 'for fun' is playing with self-imposed limits that are more important than winng.
And you know what?
In a sense, that's healthy. Winning isn't everything. On the other hand...
Winning is a worthy goal, and honestly, if you're gaming? It should be a goal. I mean, if you're going to play the game, aren't you by definition trying to kill the other guy and take his stuff? I mean, on the table, at least.
And, to be honest, isn't winning usually fun? And if it wasn't, was it due to the person across the table? On the other hand, you should be able to deal with losing gracefully.
Common use of 'Competitive' and/or WAAC
People seem to use 'competitive' one of two ways. Those that impose voluntary limits on what they bring are probably going to call you 'competitive' if you bring the supposedly 'harder' units. By contrast, a so-called competitive or WAAC player supposedly ONLY plays to win, and is dissatisfied by anything less.
As such, they are more likely to bring units that the 'for fun' folks will frown on. If they win against the 'for fun' folks, then it's either twice the affront (you played the game 'wrong' AND you won) or they write it off because you did it wrong.
In Other Words...
You didn't play the game someone thinks it ought to be played. That really sums it up for both sides; some folks in either camp think they've got the "One True Way." I doubt either supposed side could come to a consensus on exactly what their side is about anyway.
What We're Really All Talking About...
We're really talking about how people think about the game. At the end of the day, this is a game played by two or more people, and it's a test of your ability to get along with someone. It's also a test of yourself.
You should ask yourself...
1) Can you win gracefully?
Seriously? Can you? You may have monkey-stomped someone. Or, you might have had good dice luck, their bad luck, and any number of things. Gloating is a sure-fire way to make an ass out of yourself. Congratulate the other guy on a well-played game, or commisserate with them on craptastic dice luck. If they ask for pointers? Oblige them, but do so tactfully.
2) Can you lose gracefully?
Throwing a hissy fit is...not losing gracefully. Shrug it off. At the end of the day, it's toy soldiers, and it's not going to impact your self-worth, job, or anything else of importance. Congratulate the other guy on a win.
3) Can you be honest with yourself?
I think THIS is the biggest challenge of all. PIck apart the game, and ask why it went the way it did. Sometimes you make mistakes, sometimes they do. Sometimes the dice are the dice, and they have an undue influence. Can't win if you can't roll over a '1', can you?
4) Sense of humor, being philosophical, what-have-you.
It's life. Stuff happens. Deal with it. Usually, this is a social game we arrange, so we've a choice who we play with. Those people that are sketchy to play with? They tend not to get a lot of games. In tournaments, we don't always get the choice. Just remember that this too shall pass.
5) Are you willing to learn?
This'll be what'll help you improve your game. There is nothing wrong with improving your game.
If you can do these things, you will be fine as a player.
The Real WAAC
The real, ultimate Win At All Costs literally tries to win at all costs. We're talking a mindset willing to go out of the game's rules. They may cheat, but it's not a given. This is the mindset that's fine with being a jerk, and engaging in any kind of unpleasantness. I have heard tell of someone being enough of a jerk at a tournament that his opponent simply offered to concede because of it, and the opponent started filling in their score.
If this is you? You're doing it wrong.
Just freaking be a pleasant person to play. I guarantee you that regardless of your mindset, if two decent people get together to play a game, they'll probably enjoy it. I don't think you can realistically break it down to a simple 'Fun OR compete', as it's ultimately a game set in a rich universe, and it's on the player to decide what they want out of it.
Ask yourself if you can do some of these basic things, and exactly why you'd not like to play against something. Maybe you're not taking the counter. Or, sometimes, honestly, it's in the codex design. At the end of the day, though, it's up to the player to decide what and how much they want out of the universe. Personally, though, I think that either extreme (playing ONLY what looks neato, and playing ONLY what you think will win) means missing out on some of the hobby.