Postgres 7.3 .allows 32 arguments in the default build. That's progress one power-of-two at a time!
We'll be supporting PG 7.3 in 4.6.2 or 4.6.3 and I don't think anyone will be offended if packages you write and give back to the community requires PG 7.3. Just make sure your package .info and .xql files reflect that fact! :)