Just like the iPhone 4 before it, the feature I wanted most from the iPad 2 was support for 900 MHz UMTS/HSDPA in its 3G chipset. And just like the iPhone 4, the UMTS/GSM version of the 3G-enabled iPad 2 delivers, with the same quad-band support as the iPhone 4.
The original iPad (and the iPhone 3G and 3GS) supported three frequencies for high-speed 3G access: 850, 1900, and 2100 MHz. If a wireless provider's 3G network didn't operate at one of those frequencies, the iPad or iPhone would then fall back on EDGE, or worse yet, GPRS, at 850, 900, 1800, or 2100 MHz. In countries whose wireless providers chose to run wide swaths of their 3G networks at 900 MHz, this meant older iOS devices would have extremely slow connections anywhere outside areas running at 1900 or 2100 MHz.
As an example, my old iPhone 3G would drop to GPRS anywhere outside the central areas of major cities here in New Zealand, because my wireless provider's "extended 3G" network operates at 900 MHz. The iPhone 4 supports 900 MHz, greatly expanding my local 3G coverage compared to older iPhones, and the same will be true of the iPad 2 compared to the original iPad. As a matter of fact, the original iPad's lack of support for 900 MHz UMTS/HSDPA was one of the main reasons I didn't buy it.
Now that the iPad 2 has the same quad-band 3G capabilities as the iPhone 4, this is no longer an issue. Almost all wireless providers worldwide operate their 3G networks at a frequency now supported by the iPhone 4 and iPad 2, meaning US owners of the AT&T 3G iPad can travel internationally with few worries about network compatibility.