As far as I can tell, Advantage/Disadvantage is the 5e version of the earlier +/− Circumstantial Bonus.
I use it all the time.
Does the player effort sound plausible?
• Yes (Auto Succeed)
• Probably (Advantage)
• Maybe
• Unlikely (Disadvantage)
• No (Auto Fail)
In practice, the Advantage is worth about +2½: better than +2 and less good than +3. Advantage wins lower DCs more reliably but doesnt achieve a very high DC.
For me a Trap is moreorless the same thing as a Skill Challenge. I dont think 4e and 5e have hit on the best method to do it, yet. It is hard to make a Challenge protracted and interesting when there is little consequence beyond yes/no. It doesnt fight back. In many circumstances, success is inevitable, so failures mean amount of time spent, which often has little consequence.
In the meantime, narrative adjudication helps much. The players coming up with solutions that I didnt anticipate, and which seem plausible, allow for a kind of interactivity that can make the Skill Challenge interesting.
I place Traps sparingly, and only when narratively they seem necessary. I dont want a game of "ten foot pole" paranoia or "running chickens". But some things obviously would have a trap.