Illustrator is perfect for op art - look at some of the pieces from the 60s and see how they were put together. It's not black and white (the classic) but here's one I did a while back in Illustrator:

As for your example, Martin, I would start off with concentric circles & just add filter after filter untill you've achieved the result you want. Twist it, use the free transform tool to nudgde it a little, maybe bloat the whole thing up a little... Play around & you could come across some very surprising and nice results.

Transfrom copy in Illustrator - then Open Apple/ Command D to repeat shape - then distort etc. Move to PhotoShop for even move fun - layer them - use Liquify filter etc.

thx for the tips guys!