I got a bunch of the first gen knives. My assessment:
old v new:
handles - the new ones are better but the old handles work well. Meaning if the new handles are 100 out of 100 the old ones are an 85 out of 100. The new handles are also longer. The real difference is in the microtexturing especially with the G10 handles. I've worn out my micarta handles from 3 years ago. The new MT makes S!K scales the tackiest in the biz.
finish - I believe the new finish helps with corrosion protection but I like the look of the old DLC much better, though it actually caused the knives to stain more than if they didn't have the coating.
blade profile - GSOs over 3 years that have NOT been reprofiled don't cut and carve as well as knives that Guy was producing about 3 years ago. The new knives' blade edge below the secondary bevel is longer to make it a better carver
gimping and spine - the first gen knives had rounded gimping and a rounded spine. The new gen knives have more gimping on the spine.
pommel lanyard hole - the new gen lanyard hole in the scales is bigger, and better.
sheath - the new gen sheaths are a bit longer at the mouth - no opinion they both work well
heat treat - the new knives have improved the edge retention and is a little easier to strop
width - I believe the new knives are a touch thinner - no opinion
fasteners - the new fasteners are not screws and are easier to remove and replace
the engraving is now in house and is slightly different - I believe it's better than the knives I have that are over 3 years old
design - Guy has added some great new designs and modifications to the original design. So far I LOVE all the new design changes and the new model 4.7 is a fantastic knife. I was skeptical about it because I didn't think S!K needed another sized knife between the old 4.1, 5 and 5.1. I was wrong!