due to their very nature, gestalts are all about compromise. But as you said, the better gestalts are the ones that hold up well as individual units and in combined gestalt form. I find Predaking to be a pretty good gestalt by 1986 standards. Of course, he's also really expensive. But I find most gestalts are pretty well made. I've only bought two gestalts that disappointed me at the time of purchase:
+ 1989, when I completed Monstructor. Most underwhelming.
+ 2010, when I bought Combiner Class Devastator. F'expensively underwhelming!

Otherwise I've always been stoked with my gestalts.