They're good. I like his frizz serum and shampoos. I think that they are a little bit overpriced for what they are. I don't mind spending $24 on a fabulous shampoo (Kerastase comes to mind - in my opinion they make the most exquisite hair products sold on the luxury market), but I just didn't think that the Jonathan products were worth the price he is charging.
I also think that some products can be fabulous, but if you live in an area with lousy water, etc, it doesn't matter how great the product is.
Try and get a sample in Sephora. They're definitely good products, just not worth the price in my opinion.