Best PHP to use for 2.2?

[Shayne Hardesty]

  I'm planning an upgrade from an 2.2-pre version to the newest stable
IMP/horde version.  The server that runs imp for us doesn't run any other
PHP apps, so I don't have to worry about that.  Since I'm going to have to
recompile apache and upgrade php anyway, do you guys have an opinion as to
whether it's better to install the latest 3.x php (3.0.18), or go ahead
and upgrade to 4.x (4.0.6)?  I don't follow php development so I don't
know if the 3.x series is considered "outdated" or maybe it's more stable
than 4.x.

Thanks,
Shayne