Stained concrete looks great. I saw a liquor store that did it....

personally I love stained concrete but be aware that not everyone does
if you plan to move in next few years it is probably less expensive to have your floors tiled because that seems to be the more popular flooring choice between the two...

having concrete professionally stained can be expensive because of the coats/treatment that you choose...
the looks that really capture my attention are the ones with several shades in same color family and good wax jobs...
you also have to consider the quality of the original concrete that would be stained--some concrete is not that smooth--might have damage from construction or having carpet changed out...glue can cause discolorations when stain is added so the floor needs to be cleaned
much depends on the area that you live in--some areas are more attuned to using stained concrete...price can vary by area, the work parameters, the contractor...
some people try to do it themselves but some of the machinery is heavy and difficult to move in/use...
run some searches here
people have asked about it before