I tried it by comparing the same VM with and without that setting. Here is what I found:
With "Use Host I/O Cache" disabled, booting took 40 seconds.
With "Use Host I/O Cache" enabled, booting took 12 seconds.
With "Use Host I/O Cache" disabled, doing a mini update took a few minutes.
With "Use Host I/O Cache" enabled, doing a mini update occurred nearly instantaneously.
I'm convinced.
I tried it by comparing the same VM with and without that setting. Here is what I found:
With "Use Host I/O Cache" disabled, booting took 40 seconds.
With "Use Host I/O Cache" enabled, booting took 12 seconds.
With "Use Host I/O Cache" disabled, doing a mini update took a few minutes.
With "Use Host I/O Cache" enabled, doing a mini update occurred nearly instantaneously.
I'm convinced.