well......... my 15 year old car has some really severe water spotting on it, and truthfully, i dont think any chemical alone can take it off. i tried AIO, tried ssr1, heck, i used ssr 2.5 with my PC at max speed. im thinking that a rotary would possibly be a better option. however, i do think that steel wool is a must. then again, there may be no cure for severe waterspotting that has been baking under our hawaiian sun :ticked.
for hard water spots that wont buff out, buy some Spot-X water spot remover and about 5 or 6 of the 'no scratch' scuff pads they sell with it.., you can get it all for about $15 at Home Depot, Im pretty sure it will take atleast 90% of your waterspots off of your windows. I used it on a 4runner a while back and it turned out awesome. heres a website on how to use it..
http://spot-x.com/Hints.htm#anchor954185
