I might clay and polish a window, but I'd be cautious about waxing the front windshield. Some waxes/sealants cause smearing when you use the wipers from what I've heard. Try it on a small section first maybe.
I think it's definitely a good idea to apply something (even Rain-X maybe) to your glass to prevent spotting and etching, etc. I applied Aquapel to my windshield in the fall, and now that the weather's better I see that the unprotected areas of glass (the edges) have light waterspot etching in them while the protected areas don't. This is a brand-new replaced windshield by the way.