I like all of Kirby's work right up until about the mid 1970s (Demon, first couple years of Kamandi)at which point I believe his eyesight problems began to have an affect on his artwork.
I find his earlier GA work to have a wonderfully loose feel, perhaps reflecting his brief tenure in animation at the Fleischer Studios in the 1930s). The "hay" in the inking from the prime Simon and Kirby stuff is always a delight for me to look over too.
By the early 1960s there was some stiffening up in his work that continued to increase as he got older but he still retained such power in his imagery that it wasn't at all bothersome to me (until like I mentioned his eye problems got bad).
Some of the odd drawing quirks he developed over the years (such as squaring off the tops of fingers) were often "corrected" by his inkers and thus weren't usually noticeable too.
Best
Joe
