Perfectly acceptable or adequate. Often used to juxtapose some other problem someone hasn't considered or addressed. A: "As you can see, this will be the most advanced smart phone available on the market." B: "That's all well and good, but will it be affordable to the average consumer?" We all agree that your presentation was well and good.

Said of a situation or action that is good in some ways but not others. It's all well and good to go to class, but you need to do your homework too, especially if it counts toward your grade.