If you have Strataglass, the manufacturer strictly endorses Imar products. In fact, on new curtains, warrantee is void if any other product is used. That said, Plexus is also a very good product. Don't use either of these products until you have washed and dried your curtains first. Don't dry with a chamois, but instead, use a clean microfiber towel. (Just keep in mind that the curtains can scratch VERY easily if your cleaning materials are contaminated.)
Both Plexus and Imar products provide UV protection that furniture polishes do not, and are the way to go for longevity in addition to beauty.