When we switch the Mac/Linux bots to using apache we saw a significant reduction in the number of flaky http tests. Hopefully a newer version of Apache on Windows will have the same benefit there. It would also simplify run-webkit-tests to not need to support lighttpd.
There's a chromium.org bug for this that's been open forever:
at one point I talked to rniwa about this and he was deeply skeptical that apache2 would help; he thought we'd need to move to IIS.