I feel the Ultra Tool are great cutters.
I use those same cutters for hardmilling.
I have never run them without coolant (except for HardMilling). The AT coated cutters need to run dry, the TA work great wet.
I also have not ever cut .5 dp with a .25 cutter (nor have I ever even considered it). Well... I have cut that deep but not with UT and only with roughing cutters, the amount of deflection you will get out of the cutter means multi pass is required to finish so use a rougher anyway. Typically I would do that slot at 4500 & 15IPM - 4 passes with that cutter (but that is just me).
UT speeds and feeds (last I checked) dont have allowance for the coating and typical application is to increase the SFM by 10-12%.
As far as cost goes, Everybody knows that McMs prices are way high, but service/delivery is the best ever. I think I pay around $14 for that cutter in my crappy CDN dollars (Typically double the price of an inexpensive solid).
Not much help but those are my thoughts