Mine already has a few improvements over stock: Dr Pulley 16g Variator weights for improved primary drive range and ratio, Malossi yellow compensator spring for 500 RPM better kickdown, Malossi clutch kit with slightly stiffer springs for increased slip before lockup, Akrapovic full exhaust system (baffles fitted to avoid annoying my neighbours).
It goes very well for a 500cc 'moped', my daily 12 mile commute each way (half of it motorway) is such a doddle on a scoot and very practical with a topbox and underseat storage, handlebar muffs, heated seat and grips and a "Termoscud" (shytebag) to keep the weather off.
Unsure about the insurance as I have a multibike policy, but I would guess it adds about £150 fully comp (garaged and in a low crime area postcode.)