key_cache_division_limit , when to set it

Has anyone used key_cache_division_limit to improve performance.

So far

[URL]http://fromdual.com/warm-myisam-key-blocks[/URL]
[URL]MySQL :: delay_key_write with midpoint insertion strategy (key_cache_division_limit)

point to it being useful during very heavy writes and delay_key_write, however in practice does this work as expected?