There's a
Thread on TL about what keyboard/mouse/pad combos pros use, but a basic breakdown is:
MX Blue: BoxeR, Jinro, JulyZerg
MX Brown: FruitDealer, Liquid`Tyler, Tester
MX Black: IdrA, Lyn, MadFrog, Sarens
SEM-DT35: DeMusLiM, Moon, Ret, TLO, NesTea, NaDa
Other: Dimaga (Logitech), qxc (Dell), iNcontrol (Zboard), Morrow (Microsoft)
At the end of the day the fact that big names like Moon, NaDa, and NesTea are STILL using the DT-35 implies to me that the keyboard choice itself is fairly irrelevant beyond personal taste. However pro use of blacks does indicate that blacks aren't "Bad" for rts games. There doesn't seem to be any kind of consensus among the pros over a specifically superior switch or type.