Apache 2.1 will finally add the ability to load-balance mod_proxy requests, and I trust HTTP more than a semi-orphaned protocol like FastCGI or its clones.
Until recently we were running mod_proxy on a farm of Apache 1.3 servers to funnel about 300,000 HTTP requests per day into a single multithreaded Python BaseHTTPServer process (using the PSP engine from WebWare, with the rest of WebWare ripped out), on a lowly P3/500, no less. GIL contention is probably less of an issue than many people believe in real-world applications, although it would help if there were a tool to measure it and/or something like an exponentially decaying average of the numbers of threads waiting to acquire the GIL.
And, just in case you didn't know, there is now a way to write WSGI capable applications that use FastCGI and any capable web server (apache and lighttpd). I wrote a quick howto for setting up lighttpd to use it on my weblog: