A video appeared showing that SIM locked Palm Pre’s from the UK seems to have been unlocked using a proxy SIM solution called RebelSIM. There is no further detailed information about if this is a safe unlock like with the proxy SIMs for the first gen iPhones or i RebelSIM cards use IMSI fake IDs.
In general we suppose to be cautious with proxy SIM solutions. Why? Basically it’s the same with the proxy SIM cards for iPhones (read here).
A software unlock – meaning a binary code modification of the baseband – is almost always the better solution from a technical point of view, but it on the way to being able to patch the baseband many other issues can occur.
So for people who are desperate for a Palm Pre: get yourself the german factory unlocked version and learn to live with a QWERTZ keyboard. It much less hassle imho.