I don't know if this should go under suggestions or here. I've noticed that when syncing, category info is not transferred to the handheld. This is not a big deal, but it would be nice if it did.
One other small problem I've noticed, Tasks that are all-day events on the database are assigned start times on the handheld. Again, not a big deal, but since the calendar on the Treo has the option for "No time" for events it would be helpful if that carried over.
These are two minor nits. I'm very happy with the way this works with the Treo now. It also works really well with the 2Day software I installed on the Treo.