UMTS service, most commonly called '3G', is now widely available throughout the developed world. In North America, there are only three operational UMTS networks: Rogers Wireless, T-Mobile USA, and AT&T Mobility, formerly Cingular Wireless, formerly AT&T Wireless. Coverage in Europe and Asia is almost as good as 2G networks, but there are penetration problems due to the higher wavelengths involved with UMTS than GSM or old analogue networks. AT&T and Rogers in North America use the same spectrum as their GSM networks, so they have greater coverage, but they cannot put UMTS in areas where they are short on spectrum. T-Mobile's UMTS is banished to sections of paired 1700/2100MHz spectrum, which is gleefully incompatible with every other network ever.
UMTS in its barest implementation is not very impressive. It is more efficient at using spectrum than GSM, but it needs great huge gobs of it, which is problematic for deployment in GSM frequencies. The speed of UMTS is 384Kb/s in the original implementation, which is just enough bandwidth to support two-way video calling, which has caught on just as well as every other try at video telephony and not universally supported. Nearly every UMTS network is overlaid with HSDPA, which is a higher speed standard capable of up 14Mb/s implementations. It is currently deployed at speeds up to 7.2Mb/s, with upload speeds hovering at around 200Kb/s. HSUPA is a higher speed upload standard which can theoretically go as high as 5.76Mb/s. With speeds approaching and even exceeding normal home broadband connections, HSDPA-enabled handheld PCs and laptop computers are now sold by a few major hardware manufacturers, and USB or expresscard adapters are becoming more common.
There are new auctions for 2600MHz spectrum in Europe and Asia scheduled for the near future-- it is likely that UMTS will find a home on those frequencies, in addition to the paired 1900/2100MHz spectrum it currently occupies. Combined with the eventual replacement of GSM with UMTS deployments in the 850MHz, 900MHz, 1800MHz, and 1900MHz bands, the so-called "Universal" Mobile Telecommunications System is going to require chipset manufacturers to support at least seven different bands for UMTS operation for true global roaming. Right now, there are only a few phones that support tri-band UMTS operation, and the UMTS chipsets are markedly more power-hungry than GSM chipsets. Despite its shortcomings, UMTS is a fairly good standard that is here to stay... at least until the next great thing comes along.