For it's time (and price) Infini-D was pretty darn good. You are correct about the render speed. While it was never really speedy in contrast to Carrara it is super slow.

It [Infini-D] had things that I liked better then Carrara

Yeah, me too. The fact that Carrara doesn't have a bevel tool is vexing to say the least. Sure you can bevel the outer edge of an object (say the letter "O") in the spline modeler but it inverts bevel on the inner edge of the letter. It's for that reason alone that Infini-D still lives on my hard drive. When I need to bevel a logo properly I import the EPS into Infini-D, bevel it there, save it and then open that ID file in Carrara. Much better results than doing it in Carrara alone.

ability to display several deferent user defined views on the screen

Do you mean the way you can customize how your work area lays out? 4 pane vs 1 pane vs 3 pane etc...?