The S46 can be handy if you travel in the sticks in the US. While GSM is available in almost all urban areas, There are many places (like northern Maine) which are still analog, let alone TDMA. So the S46 might be useful IF you live in or visit a part of the US that only offers good service on TDMA with your carrier.

Otherwise, just get a decent tri-band GSM phone, The T39 is nice although the three I have had were a bit flaky on software. I still use one as it has BT and GPRS capability, but the screen is... well, not.

One of the best almost-current phones IMHO is the SE T68i. Decent colour screen, can be setup for e-mail easily, small, good UI. Siemens UI sucks. No two Siemens phones work the same way, it seems, and there is precious little support compared to Nokia and SE.

By far the best business device I have used is my Palm/Handspring Treo 600, on the Vodafone network. I have used it around the world and it works everywhere. I can check and send e-mail on the beach in Thailand or Cape Town. Palm OS (much better than the flaky Symbian OS in my last SE P800) which means tons of useful (and cheap) software tools.

By very careful on your choice of carrier - many roam voice but not data!