I have been asked by XperiaX10iUser to post my solution to the problem i had with mismatch as i could not install this rom using xrecovery method/reboot, so here goes but please i am fairly new to this myself.
Firstly i removed all traces of xrecovery downloads from my sdcard and also busybox and Eminence.
I re rooted my phone using z4root, i installed xrecovery using the newer version as i was still using 0.1 release and re installed busybox using titanium backup, i then using root explorer made a new exrecovery folder on my sdcard opened that and made a new backup folder.
This time i downloaded the Eminence rom to my pc, unzipped it then copied Eminence using my phone connected to pc companion file manager to the new folder xrecovery/backup pasted there.
I then as normal went into the exrecovery boot menu and option reboot Eminence and this time it installed with no mismatch error.
As i said earlier i am new to this myself and i do not know which part of what i did put things right but i got there in the end by doing the above mentioned, please excuse my poor attempt at explaining it but if it helps somebody else/or somebody else can maybe explain better what i have done please feel free to do so-thanks.