Why are all you people fighting the superior Airbus logic??? Don't you know the airbus is smarter than all of you? It knows better, and you are just a distraction to how it wants to fly anyway. You are only one of about 30 inputs and it will decide what is best for you. Release yourself to Fifi and she will take care of you. Or not. It all depends on whether she has recalculated properly, or got hung up on some simple math. It's French math.

In all seriousness, like someone said, it will honor a constraint within 250 feet. The FAA has certified this airplane to fly in our airspace like this, so they have deemed the amount acceptable. In managed mode, the airplane flies a vertical line from point to point, and selecting increased speed will not alter that line, it will just make you go faster along it. If you are concerned about overshooting a constraint too high, you can always dial the constraint altitude into the FCU and pull for OPEN DESCENT. When it levels off and crosses the constraint, dial in the next constraint altitude, and so on. It's a little more work, but it's available if you're concerned you won't make the restriction. And don't be afraid to use the speed brakes (only in open descent). When I first got on the bus, the Captains' attitudes were "speed brakes are for sissies." That attitude has changed, and I use them frequently at certain airports who like to slam dunk you *cough* Detroit *cough*. And remember to enjoy flying the bus. Just don't let it make you lazy.