One thing I've noticed as I've gotten more pages in my site (near 500) is that the page manager becomes rather slow in all ways, especially when you edit a file's details or move a file.
Don't know if this is an area you have already looked into for optimizing speed but I thought I might mention it.
Site performance is great. The only slow down I notice is the Page Manager. Can't say that anywhere else is affected, even slightly, by the number of pages, and I have a lot of redirects due to people linking into the site with partial URLs.
Nearly all 500 pages are in the 'main menu/site map' as would be expected. . . and I still have about 250 pages to add — I'm way behind lol
It's the 'main menu' that takes the hit on performance. No real way to work around it as it is the site map as well.
I have a lot of redirects due to people linking into the site with partial URLs
Just an FYI, there's a new feature in 3.0b1 that will automatically redirect requests to an existing page if the request is similar to an existing page. The similarity tolerance is a setting in the configuration labeled "Auto Redirect Percent" and the Missing Link admin page will show you the similarity of your existing redirects.