Try Gel-gloss from Home Depot or similar store.
It'll rub pretty much everything off your glass and leave a very smooth, silky finish. Unless the spots are actually pits.
If they're tree sap, try "Goof off" or "Goo gone".
What are you using to clean your windows now?
2004 E60 530is, Delivered 12/12/03, TiSilver/LGrey, PP, SP,PS, PDC, ACC, FRS, Step, Xenons, clear bra, body colored rear inserts. (Retired, 1983 henna red 320is)
2004 Corvette Z06 Commemorative Edition