I don't know about FC2, but, FC3 is currently at 2.2.13 and current
OpenLDAP release is 2.2.23. As such, you're probably fine with FC3
openldap as shipped. I suspect the FC3 RPMs would work on FC2, since
both use the same kernel and mostly the same libraries.
FWIW, the upgrade from RH9 and FC2 to FC3 has been near painless for me on
multiple systems (no reinstall, just in-place upgrade by booting FC3
disks and upgrading existing install).
Issues to watch out for:
Apache goes from 1.* to 2.* -- some changes to suexec and modperl
Changes to SASL
Everything else went pretty smoothly on the systems I've dealt with.