Bad news - I have an omax protomax and for the thing's it's meant for, it's the Bees Knees with Ice Cream. Once you grok the slightly funky software (which won't be hard) you can go from a .dxf to cutting a part Very Quickly - faster than anything I've ever owned for one-offs. (I've not owned a cnc plasma and my marking laser is a little slower to get going though it does a slightly different thing.)
Worse news - the protomax is strictly 12" x 12", and I'd been wishing for a sort of 2' x 4' machine, and didn't realize one had appeared in the Omax lineup - you just pointed it out to me, thank you, you destroyer of budget plans you!
SERIOUS COMMENTARY:
1. Yes look at other vendors, but OMAX is a fine choice. Wardjet has a similar size machine. I don't know about FLOW.
2. Waterjet's are as incrementally expensive to run (cost per hour) as a machine can get - media costs, pump costs, etc. Laser is cheaper, if plasma is good enough plasma can be cheaper, etc. There are import lasers now that at least seem credible (a member here has posted videos of one) Plasma tables are a well known technology. Make sure the running cost of the WJ is justified by the application. (You going to cut wood, cermic, tungsten, etc? You going to cut say 1" thick material from time to time (think blanks for milling that are near net in 1 direction.) WJ will win. But if all you will ever do is cut "sheet metal" you should think about lasers and plasma.
EDIT: On review I see you want to cut 2" near-net shapes in aluminum for the mills - it will be QUITE the laser that can do that, and QUITE the plasma - so at the list price on the web site the OMAX would be a dominating entry.
3. But - for a given thickness capabilty (as opposed to running cost) waterjets are cheap. So if you are running few hours the WJ may win.
4. The list of things a waterjet *won't* cut is really short. As materials get thicker it's usefulness becomes more competitive - the sort of laser that can cut 2" aluminum is a pretty wild machine - not a problem for most waterjets. (My little protomax is mechanically limited to 1" thick material - but 1" thick aluminum, steel, etc. - no problem....)
5. They make a mess. It's not about the water, it's the media (sand) - and handling of it. A protomax is well enclosed - I'd make sure whatever machine you put in your cell is too. Remember you will need to drain water as well as supply it - but note that the volume of water is pretty small - normal tap and drain keep up with it fine.
6. The pumps are Righteous Powerful devices, and can be loud. Though my little protomax (smaller class of pump) is no worse than the hydraulic pumps on my milling machine..
