ORIGINAL: OGiii
I took a similar view to Richard partly because I didn't fancy paying the OTT OPC servicing prices. I know you can legally have the car serviced to OPC spec at an Independent and not affect your warranty but that just sounds like trouble to me.
I choose the Hartech Lifetime maintenance plan (www.hartech.org). The beauty of this is that I pay them ~£80 per month (so similar cost to the Porsche Warranty) but for that the car gets serviced twice a year 'free', they do the annual MOT 'free' and they cover the cost of ALL labour for virtually everything INCLUDING wear and tear - I just pay for parts. So for example, when the brakes need replacing I pay for the pads, they fit them free. If, as in Richards example, the engine goes pop I'll have to pay for the replacement/2nd hand engine but they won't charge the labour to fit it.
To give you a real world example, my engine did go pop and I was convinced it would need replacing (this was a year or so ago at appx 85,000 miles), the car was towed to Hartech (£59 per year breakdown cover with Europe Assistance/Quoteline Direct including full European cover) they stripped it and found a broken valve spring. Whilst it was in bits they replaced all the springs and did a few more bits while they had it all apart. I got the car back running better than ever with a bill for the springs (a couple of quid each), oil and bits - a couple of hundred quid if I remember. It would have been cheaper and easier for them to have just swapped the engine but they do the job properly. Lucky for me they are also developing fixes for the 996 3.4 engine which significantly reduces the cost of repair even if there is the dreaded cracked liners etc.
I think I've got the best of both worlds!