Hi Ken,
Not only air supply, but the gun and nozzle.
I purchased a cheap Chinese cabinet set-up that worked only so-so, then a friend put me onto a US-made gun with replaceable nozzle (either steel or ceramic) and a new 'anti-kink' pick-up hose. It now works really well for short sessions, and for long sessions so long as I keep the air supply dry. I have three small condensers and a condensing chamber in the line, and run the pipe from the compressor through a cold-water bath (5 gal bucket with ice bricks) on its way to the condenser. Works a treat at keeping the air dry over a prolonged period of blasting.
The mob I got the gun, etc from was TPT Tools:
http://www.tptools.com/Sandblast-Cab...-Supplies.html
Nathan: how do you catch the sand blasting medium for re-use?
Mike