It does work, the problem come sin with the initial whatsapp setup, it actually requires BIS for initial setup as the phone defaults the settings to BIS and until its setup you cannot get it to connect, not even with using WiFi.
When my mom got a new berry we decided screw BIS as for me it was so easy to not use it, but that cause i had BIS setup when i made the choice to not use it. Whatsapp had already been setup so it was a simple matter of changing a setting before removing BIS, problem is though then it chows your battery to know end as without BIS it has no push access so it polls the server every few seconds looking for message using data for every connect. On a berry it would actually work out better to use it with BIS than without as the battery life will be seriously impacted, my moms battery lasted a business day and mine not much longer.
It uses a few kb every few seconds to check so through a month it will most likely end up costing the same if not more to use whatsapp in pull mode instead of with BIS and getting push mode.