I have zero experience but am going to be getting some... gonna put up an instance and see how it does.
Unfortunately, the lighttpd forum (run on lighty) was down for a couple days
, but it's up again and I just received a response from a guy who has something akin to me - a front end box load-balancing into a cluster of machines for rendering - he has lighty running as his rendering machines and says he is handling 10s of millions of surfers per month... also asserts that when I get into the lighty way of URL rewriting (as opposed to mod_rewrite) that will be a sale feature enough all on its own.
It's not a terribly high priority for me but is in the works... I'll post here as I learn. I also would love to hear from anyone with experience with it.