I tested the initial Gigapixel release using my Mac mini and filed perhaps a half-dozen defect reports. In general I was not terribly happy with how the software ran on my Mini although I thought that the resizing was done well. I was in the process of buying a Mini replacement and it came in just as the new Gigapixel version was released so it took me until today to get the new Mac up and running properly and be able to test the new version.
My first comment is that Gigapixel feels like a completely different product when run on a machine that meets the requirements for the software. It runs well on the MacBook Pro, images get resized in reasonable amounts of time and most of the defects I reported or saw reported appear to be fixed. I am much happier with the new version of the software overall, and especially how quickly images are resized on my new machine.
I still have one issue and that is the way Gigapixel handles raw images. The previous version desaturated the raw images and I am still seeing noticeable degradation in image quality if I use a raw image.
The original raw file: https://www.dropbox.com/s/j83ozciszgttg6t/OriginalRaw.jpg?dl=0
The Gigapixel output: https://www.dropbox.com/s/el20hgvp50diz7r/GigapixelOutput.jpg?dl=0
Other than that my reports have apparently been addressed.