I got sick of riding my road bike with the gears so worn that they would skip when I tried to ride this poor beast up hills. I decided it was high time to upgrade the entire drivetrain (minus the front derailleur and both shifters). This cost me roughly $150 in parts and shipping, but I'm very happy with the result. I took her out riding today for the first time since replacing all the gears, chain and rear derailleur and I couldn't be happier with the results.
I upped the rear cog range from a 11-28t to a 11-32t range hyperglide cog. I have been told that I should have gone with a triple chain ring in front instead of going for such a large spread in the 8 gear cog, but I just don't like a triple on anything that isn't a mountain bike. It looks weirder to me than having a long cage rear derailleur does and it's simpler to operate when I'm exhausted. I had to put a Shimano 105 long cage rear derailleur in place of the very worn and beaten down RX-100 because of the large number of teeth on the new rear cog. 28t rear cogs are the max for the compact rear derailleurs. I went with new 53/39t front chainrings and a NOS 8-speed chain. Man this thing is nice now. Shifting is crisp, smooth and quiet.