The exploid method to ROOT your Xperia Mini Pro is fine for Android 1.6 but it will not allow flashing the ROM to change the bootloader i.e. to load Android 2.1 or 2.2 on to the device right now. With the anticipated Android update coming from Sony Ericsson very soon, it is likely the exploid root will be patched.
On the XDA forums a user called Bin4ry is currently working on finding a method of properly rooting the device. When it is announced as discovered I will provide coverage on my blog, but for the absolute latest breaking news get yourself registered on the XDA forum.
Currently there are no custom Android 2.1 and 2.2 ROMs for the Xperia Mini / Mini Pro, so that is another thing the community of owners are waiting for.