Describing physcial traits of characters - necessary or not?

O.M.G I've returned!!

So here's a topic that just popped up while I was lurking on the SYW (share your work) boards over on Absolute Write's website. I notice there's this habit to describe the MC's physical traits in the first chapter - even when it's in first-person (conveniently enough there's always something to reflect their looks). It bugs me though because it puts the breaks down on the tension, that very tension you need to launch the reader into the 2nd chapter. Sure, you might be able to pick it back up after the lump of description, but I think it's making it harder on yourself [the writer]. Even if it's only a sentence or two, if your first chapter is something actiony or mysterious, I just don't see a good point for your character to stop and think 'hmm, I should really put my brown hair up, it would go good with my green eyes'.

I get it, that writer's want their readers to get a good idea about what the character looks like so they can have a clear picture, but I'm in the camp that says it doesn't matter if your character has blue eyes or hazel eyes, whether they're blond or brunette, whether they wear jeans or leather pants - the story would still go on. Unless of course your character's mission of saving the world hinges on his raven black hair and six-foot statue.

There are of course exceptions, such as the fact that your character isn't human, but instead, a six-headed beast with tentacles, that should be mentioned up front. Of course if a character has an unusual trait that no one else in the world has, it is bound to attract attention, making the character feel self-conscience in which they'd comment: 'these people act like they've never seen a two-headed girl before.'

But I do recognize that readers like to get a mental picture of the characters they're following. I'm still not for dumping a paragraph worth of description at their feet but I can throw them a bone. The best way IMO is to slip it in subtly when the characters is interacting with others. If character A is your MC and they're a foot shorter than character B, you can insert: 'B towered over A, making A feel like a mouse.'
Granted this is relative to the character's POV, but if the story is written in 1st-person or limited 3rd-person then everything is going to be relative to your character.

But that's just my thoughts. (yes, I'm having fun with smilies - can you tell?)