I find myself in a tricky situation here. As you will no doubt have seen on MoDaCo.com and MSMobileNews.com plus several other sites, a new apparently fully working SIM Unlocking utility for the 1.6 OS is available at SmartEase.net (English translation here).
Although I can’t really hide the fact that it can be done, as you’ll find out somehow, I’d ask you all to remember that by doing this you’re probably going to damage the revenue of your home network, who gave you a heavily discounted handset which can do some really excellent things. You will also be totally unsupported as far as GPRS / MMS and SMS issues go. Networks like Orange, AT&T and Smart etc BROUGHT the Microsoft Smartphone to you, so think carefully if you’re going to do this to switch to a network that isn’t concerned with the platform.