When I read all of the glowing reviews about this extension, I was skeptical that it would live up to my expectations. I'm happy to say that it has, and then some.
I have been trying to create a instant price quote form for my commercial photography business. I had previously used RSForm!Pro by RSJoomla!, but found it a little too complicated and quirky to complete the quote functionality, so I simply gave up. (Note: RSForm!Pro is an excellent extension; I simply found it to be a little more than I needed for a basic quote form).
What I like about Calc Builder is that it is simple to use for basic calculators, but has enough additional capability to do some really slick things. For under US$30, it's really quite handy.
Moonsoft's support is exemplary. I had some difficulty getting started with my first calculator because the interface is different from RSForm!Pro. I simply created a couple of support tickets and a couple of forum posts, and I received helpful answers VERY quickly.
The only shortcoming that I can think of is that there is no way to design separate user and admin emails as in RSForm!Pro, which somewhat limits how Calc Builder can be used. That said, this is a great extensions and, for the price, an excellent value.