What load balancing software do you use ?
brianr: I'm using nginx in a couple different setups:  nginx -> paste (pylons)
nginx on one machine, three other machines with 8 instances of paste each. Nginx proxies directly to the paste port (which incidentally is also itself a threaded server, but I've gotten best results by running several instance per box). Volume has been as high as ~8mm dynamic requests/day.  nginx -> lighttpd -> php-fcgi
nginx on its own box proxying to 8 app servers each running 160 php-fcgi instances. Volume here is ~16mm dynamic requests/day.Both have worked pretty well so far. As anortherjesse said, there's not a lot of feedback, but it's done everything I need so far.