I use linoleum in mine - easy to clean and I picked up from someone who was renovating their kitchen for nothing. I also use a rubber mat (a car mat actually) to take the strain off the feet, which cost about $5.00.
My floor is concrete and standing all day without the mat used to end up killing my knees; best $5.00 I've spent on darkroom gear!!
I have my Ilford MC 500 up on a small stepstool (and the spare as well, actually it sits on one of those flower pot bases with rolling casters - these things are QUITE heavy) so that in case of flooding, my electronics aren't sitting on the ground.
Concrete floor and linoleum,have no need for anyting more.
(BTW tired to have all the colour in the darkroom as close as possible to the darkroom light such that reflected light from various sources would reflect fogging light as little as possible, ans still give light!)
/Bertil
Mine is plain old concrete. It works well, but it's hard on the back. I could put down some interlocking resilient pads in the heavy work area, and I may. But those can be hard to keep clean. Linoleum sounds like an excellent idea.