Sylvieg wrote a script which I used to import 500 000 (!) wiki pages.
It needs a clean up (permission checking) and will be released.
You can already prepare your CSV file according to:
"The file must be a csv file and must contain all or some of the fields: name, hits, data, lastModif, comment, user, ip, description,lang,category. A cvs file has a first line describing the fields separated by comma, and each next line is a data with the values of the fields separated by comma ( if a value has a comma put the value between double-quotes and if it has double-quote, double the double-quotes. The page is only created if it does not exist. The category must exist. The category can be added to an already existing page."
Please ping me if you don't see the script here within 2-3 days...