Om has the news about AT&T "deciding" to open up their 3G networks to apps like Skype and client Truphone.
That said, having made calls over 3G in Europe, I wouldn't begin to jump up and down so fast. If you're standing still or walking it will work, but my last attempt (at 220 km/h) in Austria connected but I was outrunning the switching between cell towers along the autobahn.
Now, my take. This had to happen. AT&T is spending a fortune on their 3G update, with estimates being between 7 and 11 billion dollars. To get more usage of the upgraded 3G network really is a way to get people to realize you can do more, and VoIP is an already known application that works over data networks, so their "deciding" is really more of them capitulating now, when the network is more ready.
But this becomes far more interesting when T-Mobile, Verizon and Sprint all say, they will do the same thing. Yesterday at the Andy Seybold Wireless University Application Competition, Truphone's Tom Carter demonstrated how to make calls using the Apple iPod touch and the Truphone iPod application via Sprint as he borrowed my MiFi. Last month we saw T-Mobile upgrade their 3G network coverage in more places across the USA, and we learned from Amazon that the Nokia N900 (which I have on order) will work on their network not AT&T's, and since it has a SIP stack and a VoIP client already built into the Maemo OS, I see the same calling being done on the N900 fairly soon. But only if T-Mobile does the same thing as AT&T.
Overall this is very good news, which becomes better news when all the carriers around the globe do the same thing.