It's an enjoyable change of pace from Batman's play style. Catwoman can't take as much damage and the climbing mechanic takes a little getting used to, but her greater agility and the ability to crawl upside down on grates offsets that. I find that I have loads more fun playing as her in brawls as well. Half the fun is just watching the crazy moves she can pull off. Of course, it probably helps that I find her *ahem* easy on the eyes.
I find her abilities to be lacking during Predator segments, however. It's harder to make a quick getaway without tools like the grapnel gun and zip line, and you're in for a world of hurt if they start shooting you.
In all, I'd say it's worth the purchase if you plan on exploring everything the game has to offer.