SO I did a little routine maintenance on Sunday including installing a new chain. My old SRAM PC-1031 chain had about 2000 miles on it and was somewhere between 0.5 and 0.75% stretched according to Park tools.
Everybody and their dog seems to recommend KMC chains (and I believe KMC OEM's the other main recommendation - Shimano chains) so I purchased a fancy one - X10SL or some such thing, from Amazon. It has fancy little X-shaped cutouts in the side plates which purportedly leads to better shifting.
I finally hopped on the bike for a short ride tonight after sunset and really... the shifting was better, possibly just because it's a new, unstretched chain, but the new chain is SIGNIFICANTLY quieter than the old one. Although it's possible that's just because it's new, my old chain was never this quiet. I like quiet.
Anyway, thumbs up for KMC chains.