This is my take on web servers. After almost three years of large heavy web-hosting missions for real high-availability for financial institutions and so-called web 2.0 companies, I do not see any further a big interest for Lighttpd, but I have rather seen and do more and more see interest for nginx.
While corporate mostly tend to stick to Apache/IIS, many are now using Nginx to speed-up static content but as well dynamic content. I have actually done some benchmarking for a large PHP website and using Nginx with PHP-FPM vs. Apache with mod_php or suPHP with heavy tuning turned Nginx to clear 30-35% gain on dynamic pages.
Not to mention – in a very large setup, I even had Nginx talking directly with Memcached for serving dynamic cached content and this was just a killer feature. The proxy features of Nginx, while not as rich as Varnish for instance are just awesome (those who want to do that, be sure to know what you do and master the structure of your indexes). What does and will suck, is that Nginx does not have anything like .htaccess files - but once you get used to write Nginx, you won't go back to writing htaccess.
My honest opinion – DA should give us the option to have Nginx + PHP-FPM as an option to the current old but savvy Apache stack, which should also stay.