I think even with the ESID of things, it's not a bad gig. JETs have a guaranteed salary and healthcare and insurance. That's more than a lot of people working in any country can say. Yes there are some placements that seem better than others, and I'm sure there are some placements that are truly horrible... but from what I can tell those are few and far between.
For example, comparing my situation to another person in the same BoE as me and another BoE:
I live in a super rural place (1300 people, 40 minute drive to the nearest city and train stop), there is nothing to do in my village, no other English speakers, I live in a run-down, dirty, old teachers apartment building, and don't really have any friends. However, I know all of my kids by name, I only have two schools to teach in, I'm becoming really good friends with my fellow teachers, my Japanese is improving hugely, and I don't pay any rent, for a dirty, old, rundown apartment that is still bigger than many other's I've seen.
Friend one lives in the city that is 40 minutes away from me and works for the same BoE. His apartment is about a third the size of mine but is new and very clean and nice and right in the center of town. He's surrounded by the other 9 ALTs in the area within easy walking or biking distance, he can do whatever he wants whenever he wants, and he has a social life, his rent is also free. However, he doesn't know his students' names, he teaches at 4 schools, and he doesn't have any Japanese friends really. He doesn't really know any of his teachers, and his transportation, food, and electricity bills are higher than mine.
Friend two lives in the next city over and works for a different BoE. She has a HUGE apartment that was just built last year or so, she has teachers who care about her and has been learning a lot of Japanese though she is pretty rural as well. She has 4 conbini within easy walking distance and a number of places she can go out to at night if she wants to have fun. However, she pays 5 man in rent every month, doesn't know her students names, works at 3 schools, and is rather isolated from other English speakers.
When I saw Friend two's apartment, I'll admit, I was really jealous of it -- however, I think that my perks make up for what she has that I don't. I think that ESID can be frustrating at times, but no matter what the ups are of someone else's placement, I'm sure there are things that they would envy about your own. Every situation has pros and cons. I've only heard of one or two truly terrible placements with no redeeming qualities.
When I first got here I was really worried about it... I'm a city girl born and bred and so living in such a tiny village worried me... a lot. But it's turned out okay. Would I choose to live somewhere like this if it were up to me? No, but I don't mind staying here for a while. It's all in the perspective in how you look at things. If I focused my thoughts on the negatives instead of the positives, I would be absolutely miserable. Instead, I prefer to focus on the things that make my placement fantastic and let the negatives roll off my back.
Over all, I think that JET is a pretty damn good gig.... especially for those participants who are fresh out of college -- there's no where (at least not in the states) that a fresh college graduate will get a job with full benefits, paid vacation of 10-30 days a year, sick days, housing assistance, and a salary of close to 42K (us $) a year. With that in mind, I think even the less favorable parts of the job are easily tolerable.
But maybe that's just me.....