MrMoto welcome aboard... I have had my 03' SERK for over a year and have not had any problems. My close friend also has one and not any probs either. Your gonna love it....
Naitram is right, $619 sounds high to me as well. I think I paid that for three years when I bought the bike. As for if you should do it or not, that's up to you. If you plan on making some major modifications to your scoot, most likely your warranty will be voided. But check with your local dealer who will be servicing your bike. Some dealers will void it with pipes, high flow air cleaner and aftermarket pipes. Luckily mine will still stand behind the extended warranty with these mods. The catch is they have to install the mods. Ok with me since they are good people and their service is awesome.
Good Luck!