We used to bring 30 remote MS-SQL databases, together with some Access data, into MYSQL so we could do some central reporting and it was an automated process of dumping out CSV files and then imports with some stored procedures to modify the data as requied.
It took some work to get things going, but then the process was a daily, automated run - so don't rule out the csv route. While deciding what to do, we did try some commercial convertor products (dbconvert) - which duplicated things very well but did not give us the flexibility of our scripted work.
If you are just concerned about manual aspects of the conversion, you might want to check out the Open Source shellsql tools that did most of our MS-SQL dumping for us:
I daresay I could dig out some of the scripts I wrote if you want to investigate further.