First off, the ACPP is plain old vanilla "insurance", its called piece of mind in that anything happens to your Mac (but please read what is covered and what is not) you can scream, shout and b**** to Apple to get it fixed.

You might wanna skip purchasing an ACPP for your iMac but if you lug your MB around, I think it is a good idea to at least spend your hard earned cash on getting one for it, since as a portbale unit it will get a lot of wear, carry and tear.

Lastly, SHOP AROUND for your ACPP. Basicly, what you are buying is a bunch of NUMBERS. Let me repeat this: SHOP AROUND.

Inside the ACPP box is some bunch of papers and a CD (some sort of diagnostics application I never bother installing). THATS ALL. The important part of the mostly empty box is the ACPP number which is required to tie your Mac's serial number to the ACPP you bought. So buy from a reliable source, and shop around for the best price.

A general rule is, if you machine (Mac+PC or anything electrical) works great for 6 months, it will work great until something major happens (lighting, drop from the sky, you poke it with a knife, etc). My 1st Mac Mini died within a month (bad mutha-board), and I got it replaced with a new one (its still working after 2 years plus and yes I did bought an ACPP for it).

Hope this helps...

I mentioned skipping the iMac since the iMac gets less used and abused unlike a portable, so that will save you some bundle of cash. But if you insist....

On another note: Dell has the optional Complete Cover protection plan on their machines, which covers spills and accidents as well. So if you are a clumsy person or was cursed by a powerful witch, this is a good idea to get...