I like simple. I like rolling dice. Adv/dis is a great rule for those that like those things, like me.
Some people want a more "realistic" model, with more granularity, for bonuses/penalties. Fair enough. Myself, I find that too complex for a same in-game result.
Think about the following example : when passing from 3E to 4E, a lot of discussion turned around the calculation of diagonal movement. In 3E, one diagonal square counts for 1.5 horizontal/vertical squares. In 4E, any movement is 1 square. After having played extensively in both editions, I can honestly say that the 1 for 1 diagonal 4E model is really quite fine and our group had absolutely no trouble using that as an abstraction for diagonal movement. This, even though the 3E model was more realistic.
Let's get on with the gaming, and cut down on the number crunching, during game sessions. I think that Adv/Dis is just that : do away with more complex calculations and get it done already.
Will the rogue have a greater bonus in some circumstances than he would have had with a greater granularity system? Maybe. What will that change, when an adventure is all done? What moments will you remember, what events will stand out? The discussions around "wait, do I get +1 or +2?"; or the discussions around "hell, when my rogue managed to trick the dragon, wasn't that great?" Adv/Dis allows those last moments to be reached more quickly, at a reasonable expense or verisimilitude (or insert here whatever the concept you wish your game to have

). And I get to roll more d20's.
I'm all in.