I’ve got the same problem. WP 2.6.3 was running fine. Upgrade to 2.7 and now it’s take over 1 minute to load the main page whereas before it was a second or 2. And it’s definitely not my server because I still have another 2.6.3 blog on that same server and it flies.
I’m not familiar enough with this stuff to be able to diagnose the problems, but I’m on a shared linux hosting plan with 1and1 and I’m having horrible slowness with 2.7.
And mods like Otto make me want to leave WP altogether. This seemed like such a helpful and cooperative community but his attitude has totally soured me. Telling everyone their servers are broken and funky is not helpful. Less confrontational and dramatic language would have been much more helpful.