If you don't need transactions, then MySQL with the MyISAM engine has several aspects I love:

1: Blazingly fast. As it simply hands DB writes to the OS and benefits from all the caching and optimization the OS does. Depending on your storage medium, insert/updates/deletes often are 100x faster then with an ACID compliant engine.

2: Simple data structure. Want to see the sizes of your tables? "ls /var/lib/mysql/your_database" and you see each table as two files. One for the data, one for the indexes.

3: Easy to copy the data "cp -r /var/lib/mysql/your_database somewhere" and you are done.