Solved the problem, Michael, I'm happy to say.

I had the mesh angle turned down to a very low value. I also swithed off "detail to inflections" and now the fillets happen super fast. Nice :)

Here's another thing I found:
With some letters, S in particlar, if I fillet the vertical edges, then the top face will not fillet. It would probably be better to fillet the original 2d curves before extrusion.
EDIT I withdraw this comment. Problem solved by slightly reducing the fillet radius

By the way, it's great to be able to turn hidden lines on and off from the view menu. I don't think that feature was there in v1. And the C-plane feature will definitely come in useful.