On Unix systems with POSIX threads support, Apache can now run in a
hybrid multiprocess, multithreaded mode. This should improve
scalability.
New Build System
The build system has been rewritten from scratch to be based on
autoconf and libtool. This makes Apache's configuration system more
similar to that of other packages.
Multiprotocol Support
Apache now has some of the infrastructure in place to support serving
multiple protocols. mod_echo has been written as an example.
Better support for non-Unix platforms
Apache 2.0 should be faster and more stable on non-Unix platforms such
as BeOS, OS/2, and Windows. With the introduction of platform-specific
multiprocessing modules and the Apache Portable Runtime, these
platforms can now avoid using POSIX-emulation functions that are
sometimes buggy and always hurt performance.
New API
The API for modules has changed significantly for 2.0. Many of the
module-ordering problems from 1.3 should be gone. 2.0 does much of
this automatically, and module ordering is now done per-hook to
allow more flexibility. Also, new calls have been added that should
allow modules to do more without requiring patching of the core
Apache server.