I think it's worth it from this stand-point: you get 100% full warranty for two years for $17.50 per year. No arguments, no hand-wringing about whether you qualify.
However, I'm a gambler and would choose not to. Then again, I have an Original Kobo and a Kobo WiFi as back up ... and a Kobo Touch refurb will likely be available for under $100 if/when I needed one. And, I might not needed one. So far, all my ereaders are in tip top shape and three get used regularly (as in daily/weekly).