I shouldn't have said "mentioned" to insinuate "mentioned in passing", you are right. But no, though it plays a central role in his argument, GEB is not about Godel's incompleteness theorem (I believe Hofstadter even says as much in the preface, and he laments that readers didn't get the overall point of the book - though I don't have my copy with me to confirm, so I might be misremembering exactly what he says).
But anyway - you and anyone else of course are free to enjoy Hofstadter's explanations of Godel's incompleteness theorem - maybe you even think that it is the best/most interesting/most fun/most insightful explanation. I just mean to say that Hofstadter isn't writing this book primarily to explain technical concepts - his explanations are a means to an end. So someone who struggles to get through this book shouldn't feel bad - its main goal was never to be a "must-read for programmers" anyway.
But anyway - you and anyone else of course are free to enjoy Hofstadter's explanations of Godel's incompleteness theorem - maybe you even think that it is the best/most interesting/most fun/most insightful explanation. I just mean to say that Hofstadter isn't writing this book primarily to explain technical concepts - his explanations are a means to an end. So someone who struggles to get through this book shouldn't feel bad - its main goal was never to be a "must-read for programmers" anyway.