Can this be used on my worn, lightly scratched and dull corian countertops?

Absolutely - I use it mostly for wood refinishing , but label also states " cleans protects polises ... tile,glass, porcelain... mirrors, and all kitchen appliances". Go ahead and order it - be sure to read the label for other uses - I'm sure you'll be hooked and addicted to the stuff as I have been for many years. Another "not advertised" product that professionals swear by is "collinite 845 Insulator wax" mostly used for cars, boats & planes - but I am sure would also work. All best

I have a midcentury modern rosewood dining table and was wondering if this is a good product for maintaining the wood?

You can absolutely use OZ on your Rosewood dining table. I am a retired woodworking hobbyist who has used OZ on my own Rosewood pieces that I bought in the late 1960's. OZ is the secret of high end refinishers & antique dealers and is not advertised or found in retail stores. Apply sparingly in circular motions & finish wipe with the grain. all best

Can you use on glass shower doors

OZ container states "cleans, protects...tiles...glass,...excellent for windows.. bath fixtures.. kitchen appliances " ect. I have only used it on wood with excellent results. Better option would be "Collinite no 845 Insulator wax" used on ocean going boats, cars, airplanes etc. Have used for 40+ yrs - excellent results - give Collinite a try then do your car & other hard surfaced stuff.