Andy Abramson over at VoIP Watch thinks that Skype is being seriously subversive with its tie-up with T-Mobile in the US, allowing hotspot-based voice calling at a flat rate.
I'm not that convinced at all.
Two main reasons:
1) Inbound calls
Plus myriad other minor reasons. Apart from anything else, maybe Starbucks in the US is different, but my local one here in London plays such awful piped background music that the last thing I'd do there is make hours of calls on my mobile to my friends or important clients.