There seems to be some contradictory information on Georgian tap water around.
I was in Georgia recently (May 2012) for nearly a week, and mostly stayed in Tbilisi (in a hostel in an old building near the old town). Everyone at the hostel told me the tap water is ok, and I did drink it all the time without problems. Even the taste was ok to me.
However, I just came across a site called canidrinkthewater.org which claims the following:
Can you drink the water in Georgia? No.
If harbored, a parasite commonly known as Giardia, will settle in the intestines of infected humans and cause a number of discomforts such as diarrhea, nausea, vomiting, and abdominal cramps. That is why it is advised for people living and visiting Georgia to stay away from the local water supply. If you want to know, “is the water safe to drink in Georgia?” A strong No is the answer.
Now, I'd like to set the record straight on this. Was I just lucky for not getting ill, and were the people at the hostel wrong? Or is canidrinkthewater.org out-of-date or just plain unreliable, at least when it comes to Georgia?
(To assess the site's trustworthiness a little, I read entries on a few other countries, and those were mostly consistent with my experiences. The site does not seem to cite any sources, but it does provide a form for reporting incorrect info.)
Update: Looks like canidrinkthewater.org is gone (or replaced with some fishy/spammy site), so that part of the question is no longer relevant.