The door knobs should match the vintage of the house and the style of the interior and especially the doors. My work was mainly on antique homes so I sent the hardware out for restoration or looked for nice brass or crystal knobs. They looked in place on panel doors but would look stupid on flat doors in modern construction.
Contemporary doors seem to have a lot of lever type handles these days in different metal or even solid color finishes. They look nice to me in the correct situation. Some have a wonderful feel to them as you open the door and the inner workings do there thing. Others can rattle in my hand and wobble as you pull them back and forth perpendicular to the door.
As mentioned, shop for nice hardware and maybe not at a box store. Get decent plating or other finishes that does not look tacky. Non box store door hardware will be built better and last longer too. Pay me now or pay me later sort of argument I guess and you may never encounter it even with cheap door hardware but if it happens it will probably be when one of your kids gets locked in the bathroom because the door hardware failed.
"Daddy! Mommy! Am I going to die in here?"