I have not used prepared statements before, this looks like a great feature for repetitive queries.
So in pseudo code:
Did this on a fairly involved php page and quite honestly the data was inconclusive at best:
CASE Queries Run 1 Run 2 Run 3
Baseline 4013 41s 42s 42s
Prepare 5019 41s 40s 39s
More Optimize 4019 42s 40s 40s
I think it helped but it really went to show that the SQL part of the page was not making that much difference (this had one major table with about 42,000 rows)
This was done on a VM test server platform(linux) from the host os as the browser (Mac). Before Run 1 each time I restarted both Apache & MySQL to eliminate the possibility of caching effects.