Second, one of Diamond's premises in this essay seems to be that farming and its consequences are, directly or indirectly, the cause of the malaise in the world (over-crowding, wealth inequality, class structure, war etc).
So I think the point is that with farming you get free time, but also all the bad things mentioned above. What Diamond is arguing is that hunter/gatherers didn't have to deal with most (all?) of the negatives but still had plenty of free time to pursue their leisure. That is, civilization might not have been set back just because we didn't adopt farming. In the end, it was sheer numbers that decided the outcome, not the best method.
2. Yeah, we have overcrowding, inequality, classes, and war. There are bugs in agriculture. Overcrowding just means that most people aren't dying off quickly like they did when there wasn't farming. Inequality just means that some people are now wealthy, where before nobody was wealthy. I'd bet war happened before, too; it just happens on a larger scale now because everything happens on a larger scale now.
3. You can't do most kinds of technology, education, or pretty much any other kind of endeavor if you have to spend all your time near enough naturally growing sources of food to not spend all your time in transport. Most kinds of art and technology come from concentrating appropriate quantities of appropriate kinds of people in one place. That's the point of universities, conservatories, and, for that matter, companies. Most interesting things in the world come from concentrating people.
And he's not wrong; because farming is progress, and progress brings good things as well as bad things. But, as we're an intelligent species, we recognize bad things (yes, it takes generations) and work around them.
It is true that very few today farm, but take into account that, within the past century alone, the yield of farmers has increased by an order of magnitude, not to mention the millennia of domestication and invention before it. For most of agricultural history, the percentage of farmers was much higher than 3%.
For example, from Wikipedia's article on Roman Agriculture:
>In the Roman Empire, a typical family of 3.25 persons would need between 7-8 iugera of land to meet minimum food requirements (without animals). If a family owned animals to help cultivate land, then 20 iugera is needed. There would not be a surplus production on this farm.
You can actually gauge how advanced a post-agricultural civilization is based on the percentage of the population that works in the agricultural sector. Most thresholds of technological advance (most notably, the industrial revolution) have allowed a smaller farmer class to feed an entire society.