I still use Worldcraft 1.6a (registered) for Quake 1 mapping, because it is by far the best editor I've used for dealing with entities, multiple selections, texturing, and has the best camera controls (and ability to set up and save multiple cameras around the level) as well as visgroups, which allow you to hide things you don't want (bit of a pain to manage, but they work very well).
Radiant is the only other editor that I would consider, but some maps coming from Quark users are pretty impressive (gibbie's maps for instance).