Film cheapskates know that Arista EDU Ultra 400 was a bargain version of Kodak Tri-X 400, at least in 35mm. I'ver heard it's no longer that. Does anyone know what it is now, or at what speed it should be used at when processed in diafine?
Arista Premium 400 (135 only) is like Tri-X; EDU Ultra 400 never was. But if you're shooting anything other than 35mm, Premium isn't an option.
Ultra shoots at about 160 to 200 for moderate contrast (you'd need to pull it further if you're used to underrating Tri-X), so calling it a 400-speed film is a little optimistic.
It gets into reciprocity failure fairly early if you need to use slow shutter speeds (you don't have to get near Bulb; 1 second will need compensation). That may or may not be a problem for you, or a problem at all if you can afford to burn a couple of rolls and some chemistry to lay out a rough compensation curve.
It hates some developers, particularly HC100. It seems to love pyro and Xtol, but I know that pyro can be a problem for some people, so you'd need to take that into account.
EDU Ultra 400 isn't a bad film (in fact, the tonality and grain can be quite nice once you figure it out) it's just not what it says on the box at all.