4G LTE in reality
"Circuit switching is a lot less efficient than packet switching, that's why it's not the best for data and ultimately why it's not best for voice either. When some technical person hands their boss a piece of paper in the future indicating that they can support 10-20% more users by going entirely to packet switched VoLTE they'll see savings and do it."
CDMA and UMTS already effectively do this. I mean, you have a voice "circuit" but really it's not a dedicated timeslot or frequency, it's all virtual; the actual capacity of the cell site is interference-limited, not circuit limited (there is a limit on # of circuits but it's unreachable unless you intentionally load the site down with dead-silent phone calls). There is a symbol to indicate a whole frame is silence, and with variable bitrate voice background noise will not be transmitted full quality while your voice will. Forget 10-20%, they actually increase capacity by over 40% this way! VoLTE should still save since LTE is more efficient in terms of bits/mhz however.
"Is it just me thinking that yet-another-technology will be destroyed by commercial interests, deliberate incompatibilities, differing pricing structures and lack of co-operation?"
Frankly, I think the plan is to just keep billing voice and data just as now. Unfortunately, here in the states... MetroPCS has publicly stated they are intending LTE to lower their costs, which they plan to pass to the customer. Verizon? AT&T? US Cellular? They have increased data pricing significantly as they roll LTE. USCC for instance went from $30 for 5GB to $30 for 2GB.. ouch!
As for delays or whatever.. I have an LTE phone now. From what I've read, Verizon DOES run IMS over LTE, using CSFB to CDMA-1X for voice calls. What can I say? I don't have a 2-4 second delay; I just dialed my voicemail and it took approximately 1 second. Maybe CDMA kicks on faster than UMTS?
As for 4G<->whatever handoffs.. I guess the plan for voice is CSFB. You should realize, though, the chances are good that for the few moments the handoff takes it should be possible to run the 4G and (3G or 2G) *simultaneously*, known as a soft handoff in CDMA/UMTS world. I think this is one reason VZW is not running VoLTE, this type of handoff would require digging into both networks and without this type of handoff it'd be dropped call city.
As for data, my 4G drops back to 3G seamlessly, the 3G will kick up to 4G seamlessly due to some rig Verizon calls eHRPD (I think extended High Rate Packet Data?)...in general. I have had this not work though, instead the 4G will fade, there'll be a huge 15 or 20 second time period with no data, then the 3G will kick in. Kicking into 1X (in roaming areas -- Verizon effectively has at least 3G over their whole network...) takes about 15 or 20 seconds too.
That said these are NOT a significant problem -- we listened to slacker on a road trip (about ~1100 miles each way), I had 4G about 1/3rd of the way and on average had to reset slacker maybe every 300 miles.