Ooops, I mistyped.... I meant 4000k.
My experience with using LED bulbs in a Durst Laborator 138s, Leitz Focomat 1c and Focomat 2c:
(note: I print B&W only and cannot comment on any use for colour printing)
The light spread is equal to a traditional bulb and marginally less even compared to an Ilford Multigrade 500 system. So yes, like Tony said, there are systems that provide a more even light spread. The difference is marginal, though. One may wonder what is better: some light fall-off to the corners may be just perfect to compensate the light fall-off in the negative caused during exposure in the camera.
The LED bulbs strangely enough produce much more light, resulting in much shorter exposure times compared to traditional bulbs. I cannot explain why this is, but exposure times with an X lumen LED bulb tends to be 2 to 4 times shorter than with a (same) X lumen traditional bulb. Maybe this is due to spectral coverage differences... I don't know.
Colour temperature variation may be interesting but may also add complexity when combined with multigrade filters. I prefer not to have too many variables.
I've never tried dimmers in the darkroom but I suppose one could combine a dimmer with a LED bulb. I have such a dimmer / LED combination in my living room. I never felt a need to use in in the darkroom.
By the way, I have some very large, traditional bulbs for the L138s (or other large format enlargers): 2 Thorn 220V - 300W, 1 Atlas 220V - 200W. If anybody is interested in buying, just let me know!
