None -- the airow gun really is unique. I suppose it could be considered a pump marker, of which I have experience with various Sheridan-based pumps as well as WGP snipers.
I use a wide range of markers, from several pumps, a Tiberius 8 pistol, an AKA Viking, or a TM7.
None, maybe a red dot if you're into paintball sights
Quiet, fairly accurate, unique
Larger than normal profile, manually loaded
I picked up one of the dealer's promotional sample Airow guns at Oklahoma D-Day last June. Included was the marker and a Diamond compound bow with a 50 pound draw. I'm always looking for the next challenge and for esoteric markers for my collection, and the airow gun naturally fit into my collection as an unusual design. I paid the dealer his $250 and left with my new toy.
The Airow gun is exactly what it advertises -- a quiet, accurate paintball marker. If you are experienced with archery, this marker will come naturally to you. If you're used to traditional paintball markers, it will take some real practice in the backyard before you are up to speed and really ready to play with this marker.
With the 50 pound bow, it shoots about 230 FPS consistently. With a heavier pull, you could achieve speeds closer to normal field limits. I personally enjoy it the way it is, because you have most of the range of a normal marker while the 50 pound draw isn't so hard as to make your arm tired after a day of paintball.
I played an 8-hour scenario game with it this September, and I had a lot of fun doing it. With careful aiming, the airow gun proved to be just as accurate as any other paintball marker. It requires a new set of skills to shoot correctly, as most paintball techniques don't apply well. While it may seem impractical to many, it offers a new and unique view to paintball.
My only real complaint is that you must manually pull the bolt back to allow a paintball to chamber before drawing the bow. It would have been nice to focus only on drawing and firing the bow, but the design is pretty simple (read: reliable) the way it is.
Overall, I'm pretty happy with my purchase. It's a fun challenge, and it serves its purpose well in my collection. I want to take this to Castle Conquest sometime in the future.
If you're looking for a unique challenge to supplement your other paintball marker, this could well be the marker for you. If you're looking at a first marker or any general purpose marker, you may want to look elsewhere. This is not a marker for everyone, and as long as you keep it in the niche it belongs, it performs exceptionally well. If you try to take this outside of the niche style of play, you will not enjoy yourself nearly as much.
I'm going to give it a 9 only because nothing is perfect and I wish there had been a way for paintballs to automatically feed so the only thing you need to concentrate on is drawing and firing the bow.