8.3.3 is a maintenance release and fixes a number of problems.
from a purely postgres point of view, upgrading incrementally within a release (8.3.n to 8.3.3) doesn't necessitate a dump and restore as the internal data storage format remains the same; it's just a case of installing the new binary - this procedure can be fiddly depending on your o/s and your level of expertise.
however, it would be as well to wait for an answer here from the pg guys themselves, as i cannot speak for the compatibility of the pt app itself and 8.3.3 (all things being equal, it should be ok imho, but wait for their official response) before going ahead with the upgrade.
in any case, it would be wise to pg_dump your database anyhow before performing such an upgrade; just in case...
susan