You can download the newest version from the download page.
I posted an entry about ESCC being unable to find some cases of External Reference (also called Linked workbooks). This caused workbooks to be marked as compatible with Excel Services even though they were not.
Sherman Der and I have been able to isolate the reason for this in a sample workbook we were sent and then, with some help from Andrew Keeler about some of the internals of the Workbook.LinkSources() method, I was able to figure out a way of finding the missing references.
Please let me know if this version of the checker has any other issues.