Many are shaped somewhat differently from the classic round bend of the past and have "ergonomic" flats where your hands rest in the drops. I happen to find them very comfortable but some riders don't like them.

Bars with the new 31.8 mm center diameter are somewhat stiffer than older 25.4 or 26.0 mm bars but I don't find that very noticable. What is better about them is they have become the de facto standard for both road and MTB bars so 25.4 and 26.0 bars and stems are disappearing. You might as well be current if you are buying new components anyway.