I think I've read most if not all of Stirling novels and short stories over the years. When I was younger I really enjoyed the General series, and the Man-Kinz wars. I found the Draka books a little dark to enjoy. I used to spend a lot time on the yahoo stirling forum. Right after the first DtF book came out most of the problems that have been posted here were talked about there. At that time Stirling was an active member of that site and generally refused to listen to anyone but his fanboys. From what I understand the DtF series brought a completely different kind of reader to Stirlings works and he seems to have changed his writing to keep that group. His books are no long military sci-fi, they are mainly fantasy. If you enjoy that type of book they're not that bad. If you want the Stirling from ISOT you're going to be disappointed.
The one argument I still remember was the silly way the US military just gave up and died in the first book. Many people argued that a lot of large bases in the Midwest and West are in rural areas and should have been able to survive. He pointed out how SCA members would beat any military force because they had swords and armor and that modern military wouldn't have the skills to survive. We tried to point out that core military skills like close order drill, discipline, teamwork, and willingness to follow orders would be much harder than a group of college students whose hobby is dress up as a knight.
Also people tried to point out that his death zones were too large by pointing out the problems a generally out of shape American urban population would have moving out of the chaos of large cities on foot pushing shopping carts or on bicycles. Imagine a fat wellfare mother of 5 or the computer tech that hasn't seen his feet in years trying to walk out of New York City through the choas of a collapsing society. I always argued that by the time most urban masses realisted the government wasn't coming to help most would already be in too poor a state to start walking into the country side and robbing framers.
I agree with all that, though I can accept whatever survivors he wants for Oregon. I also think that generally the feeling of America would survive pretty well. I think you'd see people starting to reform States and then the Union over time. Granted, you'd get some people against that, but overall people in America LOVE America. Naturally that and the military stuff goes against his thesis that the modern world sucks.
I agree that I don't think he's right on death zones. I'd think generally you'd see an upper limit to how far people move away from cities based on city-size, not wider and wider areas the more population you had. Eating other people is actually REALLY rare even in situations where everyone is starving to death. We have tons of examples in history of people all dying to starvation and never giving into cannibalism, the cases going the other way are extremely rare exceptions. So I think you'd have a fixed walking/biking radius around the city, made slightly larger with more people do to in-fighting and stealing, but doubling the population won't double the distance people can go I wouldn't think. The vast, vast majority of the food would be split up among people and almost everyone would die.
Personally I like fantasy. I don't particularly mind the fantasy stuff in the books, though I don't think he went about it in a very interesting way -- heck, I felt the books were really missing out on a dragon or two (maybe a Dragonheart-esque dragon) and perhaps wizards. Or go non-magic and still keep steam-powered stuff -- or just as interesting keep electronics but lose steam power and the internal combustion engine (yeah, it would need a crazy justification, but looking at what can be done JUST with electromagnetism without explosives, steam power, or the like would be fascinating). IMHO, his fantasy is just so-so and has the annoying "hatred of the modern world."
I'd compare his fantasy to Robert Jordan's. Sure, after the first few books Jordon went on and on about nothing for page after page way too much (including doing that for an entire book later), but his fantasy DID have a past "modern" age like ours. They didn't revile it either, but it was a thing of legend and wonder. Seems to me that is how kids growing up after the Change would think of our modern civilization. An age of wonder where we made giant metal birds that dominated the skies, journeyed to the moon and far beneath the surface of the oceans, etc. Instead all kids hate the era before the change and almost every main character says bad things about it more often than not. It's really rather crazy and preachy in that way. I'm not saying modern society is perfect, but we're better now than we were in the 1950s, and better than we were in the 1900s, and better than we were in the 1850s and all that both morally and technologically. I guess I'm kind of unique in really being annoyed at his attacks on progress.