Catalyst Blending works great, even at high Def.

If you need it to look better, work with the projectionist to do a dual blend between the projectors and Catalyst simultaneously, set a blend of around 20 to 35%, leave up the alignment marks then let the projectionist work out the rest of it.

If you are working in an extreme situation with a rediculous amount of souces that need to blended, composited, PIP, pixel adds, etc..., and don't want any hastles, USE A SPYDER and don't cheap out.

You can see everything that a Spyder does here: Vistasystems

For most cases though, Cat edge blending and a combination of projectionist will/knowledge will go a long way so treat your projectionist with class.

CC