HTML5 and "fast" aren't mutually exclusive. Plenty of examples where HTML5 mobile sites are plenty fast over 3G like Quora and Asana (just two that I use often).
I don't know what you mean by "fast over 3G" but over here 3G is faster than any available ADSL plan you can get. I sometimes tether to my phone to download some contents when I'm in a hurry. I'm guessing the article is talking about sub-256kbps wifi.
3G is never meant for Live Traffic. There are latency issues and packet losses being wireless. There is no proper QOS guarantees on top of the Wireless Stack.
So never expect good skype experience or any real-time services like - Live search on 3G networks.
