Since upgrading to WP 3.0 I have had a couple of issues with loading speed.
If I haven't been on my site for 5 minutes or so, the first page load is very slow when I try to access a page.
This doesn't have to be the homepage, I can have left the page loaded on say a blog post for a few minutes then decided to go back to browsing another page.
The page load is very slow, then however if I immediately start browsing the rest of the site straight away without a break it is back to it's speedy self.
This happens both front and back end.
I am getting overhead created in the WP_options table created aswell where as with 2.9.2 i didn't.
I can repair and optimize tables but even after a few seconds of using the site again, the overhead is back.