I have an Apache server running multiple wordpress installations. I was previously running version 0.9.2.5 and getting around 1.2s page load times on http://gtmetrix.com for all sites.
As soon as I upgraded to 0.9.2.8 the page load times increased to approx 3s, the big increase was due to an extra approx 2s time to first byte wait.
If I uninstall 0.9.2.8 on one site and reinstall 0.9.2.5 the page load time drops again to 1.2s, the other sites running 0.9.2.8 still have 2s TTFB times.
Putting 0.9.2.8 back on again increases the load time.
NOTE simply deactivating the plugin didn't work, nor did uninstalling it, I had to reinstall the old version for the time to first byte times to go back to normal.