3DS is the perfect sibling system to have as a PC gamer. Got some gnarly CS:GO/Dota queue waits? Bust that motherfucker out. Steam down for the 4th time today? One click and you're pulling weeds in your town or defaulting some faries or some shit idk if that floats your boat.
I don't play mine for extended periods but I am really glad to have it there.
My old PSP (and to a lesser extent, my tablet) fills that role for me. I think it's safe to say that any handheld makes a good companion system to the PC, so long as you enjoy the games you have for it.