I also tried out the other options for page and database caching. A few tests showed up that memcache is faster than APC, so that’s where I stopped at database caching. Page caching was switched to enhanced, which I believe is a new option. The site performance graph at Google Webmaster Tools shows pretty good performance for Novermber and December (very close to 1.5 seconds) although the overall average is still up at 3.5 seconds, which in terms of Google is slower than 59% of sites. This is probably caused by the force majeures in September and October. Page load time peaked at over 7 seconds there.
One more funny fact about Google’s Site performance and Page Speed tools is the “Minimize DNS lookups” section, which most of the time shows up a single entry:
The domains of the following URLs only serve one resource each. If possible, avoid the extra DNS lookups by serving these resources from existing domains: http://www.google-analytics.com/ga.js