This app, which I've used for almost 10 years now, should really be called Graphic Master, it is so useful and full-featured. Unless you need to create vector graphics a la Adobe Illustrator or work with multiple layers simultaneously a la Photoshop, there is virtually nothing this app won't do. I use it every day, as both my main (actually, sole) image viewer, browser and converter, and as my graphics editor for any and all purposes except those I MUST reluctantly turn to a bloated monster like Illustrator or P'shop for.
GKON's a thumbnailer, a pixel editor, a photo retoucher, a graphics library manager, a formatter, a slideshower, a crop-n-scaler, a paint program, you freakin' name it.
My absolute FAVORITE thing about GKON, though, is that it somehow produces the smallest JPEGs at any given image quality/compression level out of every app I've ever tried over the last 15 years. I don't know what Lemke's doing to optimize this so much, but it sure works!
My only ideas for future improvement at this point would be:
1) Someone desperately needs to reverse-engineer AOL's darned .ART format and make a GKON plug-in for it.
2) GKON would be even more THE bad-@ss graphics app of the Mac world if it supported Photoshop-format plugins. I get frustrated that I have to fire up gargantuan old P'shop or another compatible app to use the 100s of plugins I have, and I'd kill to be able to use them in the only graphics app I actually enjoy using.
3) Images look a little distorted (i.e. slight jaggies on curves) when you have GKON display them at the max size that will fit on screen and that size happens to be between about 85 and 95% real image size. I'd like to see the display routines adjust a little better in this circumstance.
4) Support for creating ASCII art from any selected image. Just kidding!