Yes. I couldn't notice a difference.
For a breakout game you could get away with only 4 directions.
Have you ever tried aqua ball? It's an old dos game. Well years later I played it again and I released the ball only had 4 directions, I hadn't noticed when I was younger. Just found it interesting.
This is the same game with the default bouncing ball movement. If you can't notice the difference you are crazy.
I've never heard of Aqua Ball but I do not doubt it successfully uses 4 directions. It's amazing how much you can achieve with so little. But UrbanMonk, you are missing the point. This is an open source example teaching 360 degree ball movement with embedded collision detectors. Although I respect Arkanoid, I couldn't care less about it.