Hammer is okay, just kind of hard to compare with d3ed... or cryogened.. or radiant.. or ... lol
I prefer DoomEdit myself but Hammer (which is nothing more than an improved version of Worldcraft really) does have a few advantages over it:
1. It's more stable as an application. Better written, cleaner code underneath it with a better GUI.
I hate to say it but I have a hunch the code is most likely very sloppy in DoomEdit and it's riddled with memory leaks which makes it very crash-prone as your map gets bigger and bigger.
2. Hammer is a separate application from the Source engine and thus can be maintained separately from the engine.
The fact that DoomEdit is an undissociable part of the Doom3 engine is both a curse and a blessing. It's a blessing because it allows real-time render and lighting. It's a curse because Id can't release the source code of the editor since it's part of the engine. So, that eliminates any possibility of ever seeing gifted amateurs make a "GTK Radiant" flavor of DoomEdit. We are totally at Id's mercy in that regard.... and whether the stability bugs in DoomEdit will ever be fixed is anybody's guess.
Ideally, DoomEdit should have been written as a plug-in to the Doom3 engine so that the Editor code could be maintained separately from the engine code... but unfortunately, as the song goes: run.. rabbit run...
DoomEdit also has several problems:
1. DoomEdit doesn't "see" OGG sound files in the pak files (and the vast majority of them are OGG rather than WAV). It can play them fine, it just cannot recognize files with the .ogg file extension.
2. DoomEdit's model and skin selection dialogs cannot render MD5 models in the model view. The model view itself only has limited usefulness because it has no zoom feature. Using real-time lighting with only one light source doesn't help either.
3. The entity selection dialog's "editor_var ..." fields are very finicky. If you put too much text in the definitions of those in the .def files, the field is cut off abruptly
4. The texture window sometimes gets corrupted if you have too many texture shaders loaded. Probably related to memory leaks.
5. It doesn't manage system resources very well. If you have a custom gamma setting (like I do) and DoomEdit crashes, you can't restore your desktop's default gamma with your graphic card's desktop properties window. The only way to reset gamma is by rebooting.
6. It's a huge memory hog.
7. For some reason, it hates my Athlon64 FX-51 processor based machine on which it never runs for more than 5 minutes without crashing (the game by itself runs fine BTW).
8. DoomEdit sometimes corrupts your maps. This forces the designer to make daily back-ups of his maps for the whole duration of the design cycle (and keep ALL of those as separate files) otherwise he is at constant risk of losing months' worth of work.
So DoomEdit is far from perfect. But in terms of controls, productivity, texturing, etc... I agree that it's second to none once you're familiar with the numerous key/mouse button combinations. However, it's badly in need of stabillity. For all intents and purposes, it's a beta level software.
Fix those problems and THEN... you got the best damm editor in the world