MySQL table locks solution -> InnoDb / Partitions
Definitely go with InnoDB, and especially upgrade to MySQL 5.5 (if you're not already running it and if possible). There are many improvements in InnoDB performance in 5.5.

Frankly, your use-case of a table that is 10GB and 15million rows can easily be handled by InnoDB. Proper tuning is the stuff of another question though!

As a side note though, even if you partitioned it and left it as MyISAM, you would still get table-locking issues.


  For example, a SELECT from a partitioned MyISAM table causes a lock on the entire table.