Quick note : I'm still on the fence about the extended warranty... There is one thing I don't like : if you don't follow the maintenance schedule (each 20 000km in Canada so around 12K miles), the warranty does not apply.
That means you are required to do the maintenance at every interval, from the beginning of ownership, until the warranty runs out. Maintenance is now $650 CAD (prepaid plan is not available anymore, at least for me). It means that for the duration of the warranty, It will have to be done 7 times (20k, 40k, 60k, 80k, 100k, 120k, 140k).
That's $4100 for the warranty + $4550 for the maintenance. Total = $8650 (all in CAD)
If I don't take the warranty, my service center has advised me that a visit per year is enough. I drive around 35-40 000km/year. Let's use 40k for the sake of simplicity. For 160K, that's only 3 visits! AKA $1950
So, in fact, the warranty will cost me $6700 and has a deductible...
I'm almost certain I'll switch car within 3-4 years, probably for another Tesla... and I usually trade the cars... I'm pretty sure they don't really care about the extended warranty in the trade price.
I'm at 15 000km, I guess I have 5000km to decide :S