A lot of Bitcoin-based trading was going on in the foyer. People were exchanging bitcoins for cash of course, but they were also buying T-shirts, posters, Bitcoin Magazines, Casascius coins, etc. Also people were sending and receiving BTC to settle up restaurant bills. Some were buying BFL products with Bitcoins.
For many people, it was the first time they had made mobile BTC transactions. People were generating, scanning and photographing QR codes all the time. Plenty of different mobile clients were in use, including blockchain.info and InstaWallet (whose developer, Jan, was at the conference).
Internet access was reported as being crummy, mobile phone data must have been sufficient then.
I see this same challange for other mobile payment methods, and for fraud prevention they only work with mobile signal and not Wi-Fi. Bitcoin is one of the few that works with either mobile data or wi-fi. (and doesn't need to be full wi-fi either, it could be locked down to just a few bitcoin wallet sites and the port left open for bitcoin P2P.)