This is the same advice that Nokia UK tech support give out for using any Nokia as a modem on Mac OS X, so it's in no way unique to T-Mobile.

Oh, and if you're thinking of buying an E62 and don't - don't buy an E61 either if you're not living in Europe. A European handset only has a valid warranty in Europe, Nokia USA won't help you because it's not a US model, and Nokia UK won't talk to you because you're not a UK resident. If anything goes wrong (including botched software updates from the downloadable SW updater), you're pretty much shafted. I've heard that Amazon.com are selling E61s in the US - don't assume this means that it has a valid Nokia warranty or that you can get product support from Nokia. It doesn't, and you can't.

Just a word of warning, since I've seen more people than I can count fall into this trap.