But that is the problem. I hardly ever use it because it is one time consuming pain.
When working in Lightroom to use in Gigapixel you must export image from Lightroom to desktop. Go open up Gigapixel. Import to Gigapixel and let it do it's thing. Export to desktop. Open Lightroom and reimport image to Lightroom, whew..
To use Perfect Resize. Work on image in Lightroom. Edit image in Perfect Resize. Close when done and it automatically goes back into Lightroom.
I am guessing there is a reason you cannot make it a plugin but it is a killer for me. Other than that I actually like it.