No kidding. For one there's the fact that people tend to post more when they are pissed than when they are happy. When someone is angry about their work conditions (or anything else) they want to bitch about it. Bitching is therapeutic to many people. You cry about it to a sympathetic ear, it helps you feel better. However not so many people feel the need to post like you did "Well really my job is pretty good, I don't have to work long hours, and in general I find it fulfilling." They are happy so they don't feel the need.
There is also the fact that Slashdot seems a bit whinier than many places when it comes to work. I think part of this is because you get a lot of younger people who are just getting in to the workplace, some of who have had their preconceived notions shattered. They expected to be handed a high paying job just because they are who they are and find out that's not the case. Plus you get a lot of the anti-social geek types who don't every want to have to interact with an end user. Well, many of the 9-5 jobs are 9-5 for the reason that you interact with others. So if you are the type that won't do that, well then you get jobs that have crappier hours.
Finally there's the thing that I see all too often of people deciding that more money is what they need to be happy. The primary measure they use of if they'll take a job or not is how much it pays. Ok well turns out that while there is some leeway, for the most part you have to bring more to the table to get more money. This can be more experience, however that takes time to get. Time is another thing you can bring. You work more, you get paid more. This isn't a direct kind of thing though, usually. Companies don't give you a price sheet of "You make $X for Y hours of work." It is more that of two similar jobs, the one with higher pay expects more work.
So if you are always chasing the bigger paycheck, well don't be surprised if your work isn't so fulfilling. Maybe they want you to put up with a lot of shit, maybe they want you to work a lot of hours. That's part of the reason it pays so much, they have to offer additional incentive for people to do the crap they don't want to. However you also find there are jobs that are not like that, you just usually have to accept less pay.
At my job I get 22 days a year in vacation, and some other fixed holidays. It is pretty much strictly 9-5, if something does go wrong and OT is needed, taking time off in trade is fine. They are flexible with schedules so if you need to leave to do something, that's ok and so on. However, I could probably fairly easily find another job here locally that'd pay 30%-50% more. My pay is not high over all. I have decided I'd rather have better quality of life than more money.