Some people like to complain that there are no phones to permit access to all possible WCDMA bands. My response is "¿Por Qúe?" What would one do with such a phone? Do you have a roaming plan or pockets deep enough to allow gigabytes of data usage while roaming? When I got the Nokia e61 I decided I could rest in my search for my roaming phone. I think back to the days when I traveled with two Nokias: a 2110 and a 2190, one battery, one charger and one belt case. I thought that was pretty efficient.

My data stick is quad-band GPRS/EDGE (850/900/1800/1900), tri-band UMTS/HSDPA/HSUPA (850/1900/2100). That's close.

We can pick on Europe a bit. If I recall correctly, there is still some Scandinavian coverage with GSM at about 450 MHz. I've never seen any phone that supports these frequencies.

1700 MHz spectrum is just being deployed here in Canada, and 700 MHz spectrum has been auctioned in the US and will be available for cellular deployment as soon as analog TV broadcasting is turned off in the USA. Canada will follow by a couple of years.

The only reason we can get every 2.5G GSM frequency on a device is that the world has stopped adding 2.5G GSM frequencies. There are no GSM radios that do 2.5G at 1700 MHz or 2100 MHz, so there's no need for phones to support those modes.

On the one hand multiband support is nice if you buy local SIMs and so affordable data tariffs and on the other hand there are networks like Telstra's in Australia, which have a far better 3G-coverage than 2G. Just compare these two coverage maps:
UMTS850: GSM Coverage Maps | Australia | Telstra Corporation Limited (Telstra MobileNet) | Coverage Map (it's UMTS850 only, despite the map description says "3G 850 + GSM")
GSM900/1800: GSM Coverage Maps | Australia | Telstra Corporation Limited (Telstra MobileNet) | Coverage Map

If you further compare Telstra's UMTS850 coverage to the GSM coverage of Telstra's competitors...
GSM Coverage Maps | Australia | Vodafone Pacific Limited | Coverage Map
GSM Coverage Maps | Australia | Singtel Optus Limited (YES OPTUS) | Coverage Map
...you see that with a UMTS850-phone you'll get the best coverage in Australia by far.

Another advantage of UMTS is, that those networks have higher capacity, which has often allowed me to place and receive calls, when 2G networks were congested (especially during holidays or events).

I thought it was actually CDMA2000 that's deployed on 450 MHz for cheap Internet. It is deployed in about half a dozen countries though. Mostly former NMT countries.

DRNewcomb, ever thought of when 2G/GSM will be expired? We would then certainly need a device that supports all the UMTS bands in use. I see operators that are now deploying 3G on 900 MHz soon starting to cut down on 2G in that band. I guess progress has to happen at some point. We can't keep 2G around forever. Backward compatibility is why devices cost more to make every time a new band is added. I used to be in the camp of keeping the older services running back when it was just one or two bands used for 3G (2100 & 1900) but now it's just getting out of hand. We need to move forward. Sure lots of 2G devices will cease to function once 2G gets turned off but wouldn't they be obsolete anyway? Honestly, how many here regularly use phones over 7 years old, let alone phones that were out since GSM was 1st deployed (10 to 15 years now depending on country)?

Sorry for the rant. I'm going to miss my 2G devices like anyone else but I'm excited for the future of mobile development and keeping backward compatibility is affecting progress.

There are lots of devices that are less than 7 years old that don't support any 3G frequencies.

In fact, if 2G were to shut off tomorrow, I only have two devices that I could use: my iPhone 3G, and my Sony-Ericsson K610i (and the latter, only if I were somewhere that supports UMTS 2100).

That happens when a carrier has lots of 900 MHz spectrum and not enough 2100. The big problem with UMTS is that it takes 5 MHz per RF channel and a cell needs two channels (10 MHz). While you can build a 2nd rate network with just 10 MHz (one cell "color"), to build a proper system requires 30 MHz (3 "colors"). That's a lot of bandwidth. Many 1900 MHz systems in the US are built on 10 MHz licenses.

I see the replacement for 2G as being something other than UMTS. I understand that the standard actually allows channels less than 5 MHz.

You seem not to know a basic difference between GSM and UMTS: While in GSM-networks neighbouring cells must use different channels to avoid interferences and so the "Four color theorem" must be observed, in UMTS all cells use the same frequency. So 2 x 5 MHz (5 MHz for the uplink and 5 MHz for the downlink) is enough for a continious network. Of course you can add additional capacity by running a second UMTS-carrier on separate 2 x 5 MHz-channels.
In Germany all the 4 active operators have just 2 x 10 MHz in the 2100 MHz-band.

Yes, but the use of a single channel increases the noise floor and reduces the system capacity and data rate. Which is why I said "2nd rate". With GSM systems, cochannel interference will really mess things up. With CDMA it slowly degrades the system. A cumulative effect. UMTS-TDD avoids this problem by time-slicing everything.