I’ve bought an iPhone. I ordered it from a broker in Hong Kong who got it at Apple Store Hong Kong, because the iPhone sold in Hong Kong is locked to no particular mobile carriers. In Japan, you can buy an iPhone at a Softbank cell phone shop but they sell only the iPhone locked to Softbank. Softbank does offer international roaming service, but if you go out of Japan and use it with a Softbank SIM card in a foreign country they will charge tremendously high international roaming charges to your bill (It costs as high as hundreds of thousand Yen per day! Crazy!). That’s why I’ve got an unlocked iPhone so that I can freely replace a SIM card into that issued at the country I’m in when I travel abroad.

When I put a black SIM card issued by Softbank for iPhone use into the iPhone I had bought and turned it on, it recognized the SIM card and the phone number recorded in it activated. When I plugged it into my MacBook Pro, it downloaded music, photos and data via iTunes.

Of course it recognizes either a Softbank SIM card or NTT DoCoMo’s one because it’s SIM-lock-free.
I think the iPhone matches to my MacBook Pro more than any other mobile devices like Blackberry or Nokia cell phones. More than that, there are more applications for iPhone released from both Japan and other countries so it is easier to use even in Japan.
From now on the devices I use on a regular basis would be:

• iPhone with Softbank for web browsing and researches
• Nokia N82 with Softbank for talking
• Blackberry Bold 9000 with NTT DoCoMo for mailing
• Galapagosian NTT DoCoMo N906iL my employer makes me keep for emergency contact

Advice: when you use an iPhone with Softbank, you need a special SIM card designed only for iPhone (the Black SIM Card), NOT a normal SIM card for other Softbank cell phones (the Silver SIM Card). If you put a Silver SIM Card into an iPhone, you’ll have extremely high packet communications charges. To get a Black SIM Card you’ll have to buy one locked iPhone from a Softbank shop because they won’t solely issue a Black SIM Card without selling any iPhone. You may want to keep it unpacked so that you can resell it to anybody else.