Here's what I have gathered from everything I heard here and other places on the topic.
Peel N seal works great if you are not looking for perfection. Some people have problems in the heat but I've seen people from Texas post saying that it hasn't been a problem for them. So be aware that you could have problems there. Most realise it is not the best and you may need 2 layers to achieve great sound but the price is hard to beat.
Basicly, if you want perfection go with Dynamat, if you want great stuff go with other companies products and if you want good/does the trick then go with Peel n Seal.
But I have not tried any. That's just what I gathered in search of deadening my car. Hope it helps. People with experience let me know what you think.