Granted the X10 Mini has seen and tasted Android 4.0 in the form of a very alpha build via MIUI4, for those who might prefer CM9 over MIUI4 now have an alternative to turn to. According to its developer, the CM9 port is stable enough for daily use, although there are some issues with the camera, hardware/software video decoder, FM radio and DHCP over WiFI.
However if these are issues you are willing to overlook, the downloads and instructions for the CM9 ROM for the X8, X10 Mini and X10 Mini Pro can be found over at the XDA forums.