Every household should have this product. I would trade 20 bottles of Windex for one can of Sprayway. Unlike other cleaners, Sprayway is a thin white foam rather than a liquid. It actually stays in place instead of racing for the bottom like liquid solutions. The foam also makes it very easy to see what part of the glass you've sprayed and what you haven't. It dries slowly until you wipe it with a rag or paper towel, then it evaporates with astonishing speed, leaving no streaks or film whatsoever.
Although it says 'Glass Cleaner' it works as a multi-purpose cleaner. In addition to my mirrors and glass, it works wonders on my granite countertops, to wipe down walls, microwave, fixtures, furniture, computer and tv screens, stovetop, inside my refrigerator. You name it and it works. It is ammonia free and can be used on acrylics, tile, porcelain and chrome as well.
You can find Sprayway at Costco in a 4 pack for roughly $7-8. If you aren't a Costco member (shame on you), you can find it at Home Depot and Ace Hardware in individual cans. If you want to buy in bulk, check out Ebay. You can usually find a 12 pack for as little as $2.40 per can. Still not as cheap as Costco but still worth it.
I promise you - Sprayway's versatility will change how you think about cleaning. I'll grab a can and a rag and walk around my house spot cleaning most everything in sight. My one recommendation to see fantastic results on mirrors and windows, no matter what product you use, is to go back over it with a dry rag to polish it off. I also recommend only cleaning with white rags. Another speed cleaning tip. They work great on mirrors, windows, countertops, dusting, drying off toilets, polishing fixtures, wiping baseboards - basically everything. Costco has a jumbo pack of white rags for cheap. These save on using paper towels and all you have to do is throw them in the wash with bleach for the next cleaning sesh. If you go out to buy a pack, WASH THEM BEFORE USING!