I've been living here now for about 3 months or so, and have experienced no problems using my MacBook Pro, iPhone 3GS, and an iPod Touch all over the city on whatever open, free wi-fi I find. At home I use Fibertel (maybe not for much longer) with an Apple Airport base-station. All with no problems, and pretty much automatic. (Although setting up the Airport base station to work with the Fibertel modem was a bit of a pain, initially.)

Actually, a quick edit: at home I can connect the iPhone and iPod only through the Airport base station's wi-fi, not through the Fibertel modem's wi-fi directly.