A slotted (and properly reamed) bridge using unslotted pins is a good thing. Some pictures to go with oldrocker's words:
Slotted pins in unslotted bridges create big gaps at the plate for the string balls to wiggle up damaging the bridge plate and pins - preventing this is the main benefit of a slotted bridge:
illustartion by John Arnold
Slotted bridges and unslotted pins minimize this gap as Bryan's side-by-side demonstrates:
photo by Bryan Kimsey
Bridge slots are cut to individual string sizes; the slots in pins are all the same diameter: a cheaper manufacturing solution. A proper slot looks like this pin hole on a Martin D-18A:
Many quality manufacturers and luthiers slot and ream their pin holes as a matter of course. It's a good way to make guitars, and can easily be done to any guitar any time thereafter.