I was building a new site and decided to give 5.6.0.1 a shot. I use Bluehost as my hosting company. As soon as I made the switch, my page load time quadrupled and Bluehost started throttling my entire account. I followed various postings' instructions, turning caching on and off, disabling statistics etc. and nothing seemed to bring it back to an acceptable speed. So, I downgraded back to 5.5.2.1 and everything is great. I'm not sure how useful this post is other than to reiterate that there is in fact an issue with page load time in 5.6.0.1 and it caught the attention of Bluehost enough to feel the need to throttle the account.