I took "looks like an arm" to mean it would obviously have flesh on it as well. My bad. I do think, though, that RealSkinn shouldn't be the option the majority goes for when getting cyberlimbs. As far as the awe-factor, or cool-factor goes, crystal > chrome > metal and electronics > plastic > skin.
Also, pretty much any of the aforementioned options should often have shit like some light glowing through, some wires being visible. Also, judging by the illustrations in the core book alone, RealSkinn for example doesn't always cover the entire arm, but perhaps only the top side. Same with other "plating". You can see the hydraulics and wiring beneath quite often, especially in the joints. Then of course there's the noise the servos and hydraulics make.
If you've got options like the hydraulic ram, plastic covering, armor, thickened myomar and so on, or if your hands/feet have any attachments or weapons that don't look simply like hands, then all of it should be quite visible, and exactly what you'd think it would look like. Not the silly scifi where you can hide a house in a matchbox.
Depending on the situation of course, but having something look 100% human is so boring and pointless in a Cyberpunk world. Unless of course it's 1984 and you're trying to kill John Connor, but then we're not really talking about Cyberpunk anyway.