Some UK Feedback
I can offer a bit of feedback. Been an iPhone user on and off since iPhone 3G launch (apparently I was actually the first person in the country to have one working due to O2s credit check systems going down).
There's a huge problem in the UK (or at least parts of it) at the moment, down to lack of available bandwidth, and it's affecting at least 3 networks.
The problem is this - handset will connect to a local cell tower, and report that it's receiving full 3G signal. However, attempts to use data will time out, calls will frequently either drop or not connect, and texts will be delayed.
The first time I noticed this was using an iPhone 3G on O2. Didn't have a clue what was happening at the time. Took my iPhone back to the shop with details of the complaint, and remarkably they replaced it for a new handset. Didn't solve the problem but was nice to get a brand new device 8 or 9 months into my contract.
Same thing happened on 3's network, in particular when in various North East locations back in 2009, both using my mobile handset (then an HTC Magic), and using a 3 MiFi dongle. Both would display full 3G signal, but connections couldn't be made. I had many long chats with technical support at 3, and the issue was escalated to the point where I spoke to a fairly high up engineer. He stated, as I suspected, that there were so many people using 3G in these areas, that there was insufficient bandwidth available - ie, there was signal available for the handset to pick up, but not bandwidth available for the mast itself to use (am I right in thinking this is called backhaul? I only have rudimentary knowledge of this).
I'm led to believe it's almost the same as using a home wifi router - you could hypothetically connect 1000 objects to a wifi router with a 1mb connection available, and they'd all show full signal if they're within good distance of the router, but that still means you ain't going to get a connection, or if you do it'll be sporadic/patchy due to so many devices sending/receiving traffic.
3 eventually agreed to end my contracts with no early termination fees, and I moved to Orange with an iPhone 3G (again).
I'm now having the same issue again with them, but across a much wider geographical range. Get the problem all over the North East, in Cumbria, tried it in Scotland - same issue. Upgraded to iPhone 4, same issue. Ended up selling iPhone 4 for financial reasons (gutting), and bought a cheaper Android phone, same issues.
In all cases, switching to 2G stops the problem. I've now escalated to Orange, as I'm sick of paying £35 a month for 2G service (when the product sold to me was specifically billed as being a 3G device). They're excuse? There's not enough masts in the North. Brilliant. Funny how they didn't specify that at point of sale.
In my opinion (unqualified though it may be), this problem will only get worse unless the networks/carriers really throw some money at upgrading their infrastructure. More and more people are using 3G for data in this country, with smartphones increasingly becoming the norm.
I'm led to believe that following some upgrades, 3 is now much, much better than most other networks (at least in my area). Just a shame their customer service is so utterly rubbish.
Sorry for the long ramble, I don't normally post (long time lurker, only actually just registered an account), but thought this might at least provide some food for thought.