yea, ima's glass looks pretty good for P5 IMVHO.   IOR and glass is complicated in P5 and later, due to its failure to calculate entry and exit correctly for thin glass structures.  my advice for P5 is to try various IOR until it looks as good as possible, depending on whether it's thick (e.g. 1.5) or thin (e.g. 1.05) glass.  the advantage to using trans (thin) vs. refract (thick) is that the latter may produce non-intuitive shadow fx.