My flute is a Jupiter. Is that a good flute? My band instructor said that Jupiter's are naturally sharp which I've learned the hard way =) but in general, are they good flutes? As in well built, sound(once tuned), etc.

yes they are, I have worked for this co. for several years and have toured the factory and even worked with them to improve their flutes, ask your band director to define "naturally sharp", most flutes from asia are built at higher pitch, that is because in Europe and much of asia they play at A=442 or higher, so they need to accomodate that.