One of the sticking points that some people may have had in updating their Xperia X10 or X10 mini to Android 2.1 was the loss of root. Fear not though, as a number of people over at xda-developers have confirmed that they have achieved Root using the SuperOneClick tool.
There does seem to be a bug that causes the program to continuously loop, if that does happen you should simply toggle between the USB debugging mode whilst the program is running. This means you can now get access to Titanium, Barnacle as well as other very useful root apps. Click here for more information.