spiny box pufferfish.
 

I was wondering what everyone thinks about keeping these fish and if anyone has had any experience

Here is an article on them. They need a minimum 120 gallon tank as they get to be 14 inches long.
http://wetwebmedia.com/ca/volume_6/volume_6_2/puffers.

There are also many other articles on them on puffers on the same site.

yah i have currently got a 180g.

What a nice size tank. The articles say that you have to think things through.
With a predator tank you really limit the variety of fish you can have.

Picture a 180 with a variety of really colourful fish (like tangs) on the one hand and a 180 with a few drab but interesting predators.

You can keep Tangs with a Spiny Box Puffer. You can also keep Angels, Wrasses, and the list goes on. It's only as "drab" as you want it to be.

ok thanks for everyones thoughts.

The puffer gets to be 14 inches so you are limited in the size of fish you can keep.
I would agree that you can keep some tangs that are less demanding of water quality but not most of them. Angels are fussy and require pristine water conditions.
As the article notes the species are messy and you would require frequent water changes to keep the water clear.
Travis might want to keep the articles in mind if he chooses to keep them.

I guess my point is Tangs aren't the only fish that make a tank look colourful, and they too get quite large unless you're going to go with a Scopas. Even Sailfins get to be around 15". I wouldn't want someone to thing that Tangs are his only option. Almost every species has some equally vibrant fish to choose from and there are plenty of reef safe fish outside of the Tang family. For a FOWLR tank I would go as far as to say you could have even nicer looking fish than Tangs with a mix of Angels and Butterfly Fish. I have a Purple Tang getting along nicely with a Porcupine Puffer in a 180 mixed reef. I have excellent filtration, Biopellets, and skimming, zero N & P, I don't see any issues with that.

I agree.
Some reefers with large tanks like yours and Travis might unjustly accuse me of a bias towards tangs though.

I do have to admit, I was playing the devil's advocate a little. My 150 Gal SPS is Tang only territory.