The installation manual says not to exeed 150 psi.  Makes me think the stuff isn't all that sturdy.  And many guys would want to use 3/4" tubing, especially if the run is very long.  Then it starts getting expensive, too.  But it does seem easy to assemble.

The type L (?) copper (thicker walled of the two choices of tubing) 3/4" diameter I bought in February was $1.70 per foot.  The RapidAir kit with 50' of 3/4" tubing at Northern Tool costs $240.00.  Agreed, it comes with a manifold, cutting and deburring tools, some mounting clips, and a connecting fitting.  But it doesn't really seem very cheap compared to copper, except the assembly time will be a little less if one doesn't sweat (fittings) very fast.

By the way, I think the thicker walled copper will handle way more then 150# psi.