The Luci project also has it's own http server. I've been running lucittpd for some time now on a WRT54GL and ASUS WL-500g Premium. I didn't notice any significant difference in speed of the webinterface compared to the BusyBox httpd. There does seem to be a difference in memory usage though:
PID USER VSZ STAT COMMAND
787 root 3828 S /usr/bin/lucittpd
802 root 1920 S /usr/sbin/httpd -p 80 -h /www -r Sokko
So back to httpd it is. Having a choice of webserver can be beneficial, but I question the impact that roling-your-own httpd has on security. This seems like a situation where you'd be beter of using the tried and trusted tech like busybox httpd or lighttpd.