db_file_multiblock_read_count and performance

I have been testing this extensively over the last few months. I do a full table scan with a db_file_multiblock_read_count = 1 and then one = 128( i check the 10046 trace to verify i am getting this much) and I see absolutely no difference whatsoever in response time. i am doing
select count(*)
from heap_table;
I have tested this on windows xp, solaris, with EMC, netapp, and regular old cheap off the shelf hard drives. I have tested it in 8.1.7, 9.0,9.1,9.2. has anyone see a response time improvement from this parameter anywhere?

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