Interesting. How small can you go with it?
I think the smallest I have tried so far was 0.6 mm, as that's the diameter of the wire I use to make vias and I can't remember having to drill holes for anything smaller than that. Could easily go smaller if I needed, as it's really very well aligned. One of key factors is to press the PCB down firmly to the base and not let it get lifted, or moved otherwise, as the drill bit starts to go into it. The PCB moves, the drill bit breaks. Extra attention required when you drill smaller holes first to be later used as guides for larger bits: those larger bits effectively act as screws, trying to lift the board up.
I'm assuming hard alloy bits (typically tungsten carbide based), of course. They are super brittle. Steel bits are more tolerant to misalignment, but even when made of HSS, which is a wear resistant type of steel alloys, they get dulled very quickly by the glass textolite material, because, guess what, glass is hard.
BTW I have also successfully drilled half-holes with it, where the center of the hole lies right on the edge of the board. Hold the board firmly, lower the drill very very slowly, and it works just fine. The diameter was 1.0 mm in that case. This means that the lateral stiffness of this drill press is also quite decent. Might probably be used for some very simple light duty milling jobs as well, even though the RPM (about 3k/min IIRC) is nowhere near what is good for milling, but I really don't want to abuse it this way not to cause excessive wear of the axles and bearings.