I have been pleased with how Gigapixel works on normal images with moderate upsizing. I tested it using some recent cropped birding photos and was surprised at how the upsized version looked when compared to the original - the detail was so good that I could not tell that the images had been resized at all.
Since the new version was supposed to take care of how poorly the original app did with high ISO images I decided to rerun my original tests using the same high ISO images I used in my original posting on the subject and was a bit disappointed. The Moderate setting produced images that were basically the same as those from the original app and the Strong setting produced washed out colors that needed to be fixed in Photoshop. Here is an image that I combined from the original app and the new one with the new version at the top and the original on the bottom. Both were processed from he original raw using the same color profile, using the High Quality setting and 150% resizing.
While I think the upsizing functionality is great I think that high ISO images will have to be fixed before using Gigapixel as it just does not seem to do as good a job at that as I would have thought it might and the washed out colors and the image softness from the Strong processing required quite a bit of work to fix, and I was unable to do much about the resulting image softness.