Also sitting this one out
I'm with you, Andrew. I consider myself to be part of the internet revolution. I've recently binned Vodafone due to their inability to service customers in the evening ("I'm sorry, our offices are closed. You can contact us on a webform" <but don't ever expect us to reply>) and an inability to fix dodgy network equipment in my home area. I also resent being sent a text to inform me that I'm near my 500MB data limit, when my data limit is 1GB.
So now, I'm on Three. I haven't yet needed to talk to their customer service, so don't know whether or not they'll deal with me in the evenings. But with their One Plan, I now don't ever have to worry about using up too much data. Their speed is sufficient for me and I took it on with their upgrades to HSPA+ in mind. Like you say, 12Mbps will do on a proven technology.
But here's the really important bit. I'm an iPhone user, I'll freely admit. The way it looks for networks is to find the one that it thinks is best, so Wifi first, 3G followed by Edge followed by GPRS. Frankly, I don't want my phone bothering with anything that's not 3G - I'd rather not bother trying to use the internet without 3G. And as Three doesn't have any non-3G and (with, I understand some rural exceptions) no longer partners with a 2G network as backup, I don't get those frustrating times when the phone switches from 3G to E to O. And back again.
Did I mention that I didn't have to worry about how much data I'm using? And did I mention that battery life on the 3G signal is good enough?
I'll come back to this 4G when it's a bit more mature; maybe by then, I'll have had plenty of use out of my iPhone 4S and will want to upgrade. Maybe by then, I'll have plenty of things that work with whatever proprietary connector my next phone has.
Right now, the poor choice of networks with 4G, the poor choice of equipment that works with a 4G iPhone 5 and the inflated prices with limited data capacity... the odds aren't in 4G's favour.