I've got a bottle of Zippo and a bottle of Ronsonol -- the Zippo fluid seems to have less taste, but that just may be my mind because I trust the Zippo name to be better simply because it is zippo -- I have Zippo flints and wicks but not had to swap yet.
As for warranties, Zippo's warranty is absolutely no questions asked, I've seen my grandpappy send in some rubbish he found on the side of the road and got a new lighter back, because the brass (or whatever it is) plate from the bottom of the lighter still said Zippo even if everything else was just mushed metal.
As for buying fluid? Walmart never has anything when I go, head shops carry Ronsonol around here, Zippo fluid is rather cheap through the internet though, either amazon or ebay or a few online retailers.