i went to the local camera shop and they have packs of 20 polaroid 600 instant film on sale for $15 (aus.) that's considerably cheap but the catch is that it's 2 years out of date.... should i get it? what will be the pros and cons?

From my admittedly limited experience, that's about as far past date as I'd go with SX-70 type films like 600. The film is probably fine, the developing paste as well, but there's also the battery in the film pack that operates the camera; if that's dead, you'll get nothing useful from the film unless you go through the annoying and touchy procedure of (in the dark) pulling the prints out of the pack and stuffing them into another that has a good battery in it.

Now, if I've misunderstood what you're looking and these are 600-series peel-apart films (properly called Type 100, as they were originally numbered with 108, 107, etc. for the Model 100 camera), at two years past and something like 25% to 30% discount or more, I'd go for it. Camera stores generally have good storage conditions and there's no battery in the pack to worry about. The only caveat would be to look at the way they're displayed, and shy away if they've been stored on the long edge of the box; flat, or either end is okay, but if stored on the long edge, the chemicals in the pods can settle and lead to incomplete coverage when you pull the print through the rollers.

i'm still not sure if i should get the film, i might just buy it anyway it's really really cheap. and if the film doesn't work then i will get an exchange for another item. i'll enquire about the batteries too. thanks heaps. =]