I didn't have a plan for my iBook G4. After dealing with a dead hard drive two years after I bought the machine and a dead optical drive two days after the death of the hard drive, I vowed to never go without AppleCare again. (I had never had a problem with any Mac I had purchased new prior to this iBook, dating back to my LC in 1992).
My next laptop was a black MacBook, which replaced my ill-fated iBook G4 (which I later fixed on my own and gave to a family member). Everything was going fine until the case chipped to the right of the trackpad two years into ownership (apparently a very common problem on the 2006-2008 MacBooks; many I've seen have a piece of tape there). AppleCare covered the problem, and while I don't remember the numbers offhand, I believe it paid for itself with this lone repair. Had I purchased the part I would have done it myself, but having everything taken care of under (extended) warranty was a better deal in the end and often is depending on the part.
I have it on my MacBook Air and will probably continue to buy it for my future Macs. TechTool wasn't a bad throw-in and gets used on my machines to optimize disks, but I get the feeling many weren't using it. Interestingly, the MicroMat site still says TechTool Deluxe is included with AppleCare. My guess is this is either a license with MicroMat expired or Apple simply wants to get rid of another optical disc (as the original website suggests). Of course, having customers take their machines to the Genius Bar is also a way to attract customers and coerce them into buying more products while in the store.
I've never heard about the credit card warranty deal. Just make sure to read all the fine print on a credit card agreement for anything--warranty or otherwise.
Some of us, myself included, are DIYers when it comes to our Macs. However, getting both the parts and service on some of these parts is worth it, even for savvy repairmen who have worked on hundreds of computers before, mostly because of the low cost relative to how much some of these parts go for.