i used to do entire upper body in one workout.
chest, back, triceps, bicepsm, delts with good results.
however, i've been seeing much better progress splitting the routine. so now, i'll do back delts and tris on one day, legs and abs another day, and chest biceps (which is probably the easiest day) another day. with this routine my strength shot up the roof and i always feel pumped.
however, i dont think there's anything wrong with doing entire upper body in one workout as long as you're making in hurt.