We have in floor heat fired on waste oil, so I guess I've finally found  a thread I'm uniquely qualified for!  

We used 2" pinkboard underneath the concrete, and pex in the floor.  We have five primaries each divided into (I think) 8 secondaries.  I bought a 3/4 hp circulator pump on eBay....about four times what the book says I need. 

It works good.  I rebuilt the pump first thing this fall.  Because of the oversized pump, our floor, pipes, and boiler all pretty much stay the same temp, within a couple degrees anyway.  I bought a gun from one of the waste oil furnace manufacturers and built my own firebox and water jacket.

 I replaced the gun this summer, at a cost of about $700.  I think routine replacement is going to become my new maintenance program.  Pic is of the old gun.  New one is slightly different style, but identical functionally.

Without doing some calculation, I can't say exactly what our heat cost, but there is no way it is even close to the numbers people keep throwing out in every thread discussing floor heat.  $3000 would cover the whole thing, and probably cover some of the upkeep expense over the last howevermany years.  

It takes a good bit of oil to keep a sixable shop heated.  We burn about 1500 gallons per year heating 78x80 with plenty of insulation in a fairly moderate climate.