Attached is a photo from Food and Wine, showing three roasted chickens with their legs splayed. I've always been taught to truss a chicken before roasting it and these look unattractive to me. Is there a good reason NOT to truss a chicken before roasting?
I truss game hens but, in most cases, don't truss chickens. Like "acgold7" I carve in the kitchen and serve on a platter so the fact that the un-trussed bird is somewhat unattractive doesn't enter the picture. If I'm preparing a half bird with a stuffing (dressing) I sometimes lay the bird, cut side down, on a mound of dressing (usually a rice mixture) and bake it all at the same time. Under those circumstances, because I serve half bird portions (I know some folks with huge appetites) I tie or pin down the wing/leg sections for a nicer looking presentation.
It was Julia Child who said that an untrussed chicken looks wanton.
Pace Julia, I normally don't truss my birds. I truss them if they are very small, or have a stuffing that will fall out without trussing. If I were cooking a lot of birds, as restaurants do (and often recipe testers...), trussing (when done right) makes it easier to turn birds over quickly in succession; but I never cook more than 2 at a time so it's not a salient reason for me.
Otherwise, I find that trussing virtually guarantees uneven cooking that I don't care for.
I never tie up a chicken. I think it's for cosmetic purposes only. They tell you it cooks more evenly if you do but I find the opposite is true. The heat can get inside the cavity more easily if you don't. Considering the thing most people complain about is that the dark meat cooks too slowly compared to the white meat, I'd think the last thing you'd want to do is slow down the cooking of the thighs, and letting the legs splay out speeds this up.
I carve in the kitchen so no one really sees the things whole anyway.
All personal taste, really.