Since mysql schedules queries for execution in this manner:
- Write requests (like UPDATEs and DELETEs) take priority over read requests (SELECTs)
- Server performs writes FIFO manner (in the order received)
What are the benefits ?
Deadlocks can never occur with MyISAM. The MySQL server can thus manage all contention, explicit (LOCK TABLEs) or implcit (Any DML).
As long as a MyISAM table has no deleted or updated records, concurrent inserts can freely occur with impunity. That would, indeed, include INSERTs on a table that has an explicit read lock.
For any table with gaps, running OPTIMIZE TABLE would remove those gaps and allow concurrent inserts once again.
For more information, please read "MySQL 5.0 Certification Study Guide" pages 408-412 Section 29.2.