Reader J.V. asks: Would a BlackBerry with Ev-DO technology (such as the 7703e) be usable in Japan? Would a BlackBerrys on GSM/GPRS and EDGE networks be usable in Japan?

Most of the world does not use CDMA/EVDO. Most of the world tends to be GSM/GPRS/EDGE/UMTS. Japan’s NTT DoCoMo invented W-CDMA used by both FOMA used in Japan and UMTS used in a lot of places (except for most of the US where we tend to lag behind in the wireless world).

I took a look at taking my GSM/GPRS phone with me when I visited Japan back in 2005. I ended up leaving it behind. In speaking with people who visit Japan regularly, it seems that they tend to buy a phone with rechargeable SIMs (fixed number of minutes). If you read the article I wrote about my trip for O’Reilly’s MacDevCenter…
Japan Primer for the Mac Techno-Tourist

…you’ll find a section sub-titled Mobile Phones, Broadband, & Wi-Fi Hotspots that provides links to sites that discussing phone roaming options.