Hi guys,
I have been watching this thread since the beginning and decided to put in my two cents...
As soon as I upgraded to Snow Leopard, I experienced the same exact problems everyone else did. My battery said "Service Battery" all of the sudden and nothing I did helped fix it. I had just replaced my battery in February 2009 and only had 110 cycles on it, so this "Service Battery" message didn't make sense. I always calibrate my battery and do everything right, so when I saw this discussion I decided to follow it until I could find something that would work for me.
Using Time Machine, I went back to Leopard and my battery said "Normal". The only thing was that after unplugging it, my battery would drain very quickly. I also have iStatPro and it said my Battery Health was at 48%. That's not good at all, obviously. So I upgraded it again back to Snow Leopard and decided to make an appointment at Apple.
When I went to the Genuis Bar, the guy plugged in an iPod to test my battery and it came up as BAD BATTERY. He replaced my battery for free because I still have AppleCare and it was a defective battery. I asked him if Snow Leopard did this to my battery. He said Snow Leopard didn't do this, it's just that Snow Leopard told me about the bad battery whereas Leopard didn't recognize it. That's the only thing that made sense to me because Leopard still said my battery was Normal even when it wasn't. Either way, they are admitting to a flawed program if Leopard isn't able to recognize bad batteries.
Anyway, I just wanted to write my experience. I was hoping to be able to fix the problem without having to go to Apple because I am always so busy, but it ended up working out for me. I got a brand new battery, free of charge, and it hasn't said "Service Battery" since (and it's been over 2 weeks). Also, my iStatPro says that my battery health is at 100%.
So I know many people might not want to hear this, but I would suggest going to your local Apple store ASAP and get a brand new battery. Everything else on Snow Leopard has been working great for me since getting the new battery. If that changes, I will be sure to update on here.