As mentioned by Elizabeth Naramore on the php|architect site, there's a new version of the free debugger from the PhpEd folks that's been released and ready for download - version 2.15.5.
Updates in this latest version include:
- All php versions from 4.3 up to 5.2 are supported
- Fixed problem with profiler denominator
- Pre-compiled binaries for Win32 and Linux
- Source code