The general advice is that after resistance training you should consume plenty of simple carbs to spike your insulin level and thus help getting nutrients to your muscles (and to replenish your glycogen stores).
However, insulin is also responsible for storing excess calories as body fat which is clearly a bad thing and should be avoided as much as you can even when you're bulking. Recent research also indicates that you don't need to skyrocket your insulin level since it gives no extra benefit, so a low-GI food with protein (e.g. whey shake and some fruit) should also do the job.
E.g.: Alan Aragon's Research Review
So what's the truth? Should we skip simple carbs post workout?