There are people in every field that hate it. I've shadowed so many optometrists that totally love their profession...so it's mixed. Optometry isn't for everyone, and I think some people have certain expectations that aren't met later. If you do your homework and really shadow to see what the profession is like and ask all the optometrists to be very frank with you, you will get a much better idea. The ones that I have shadowed who have been more negative about the field weren't really people persons (not that I'm saying everyone who is unhappy with it fits that category - just from the ones that I shadowed), so I think that they didn't necessarily realize how much schmoozing it involved. I also think there are people who go into the field without a solid business foundation (and I think schools are making an effort to train better in that area). It's really hard to open a private practice, but it's possible. You have to make smart decisions though too...opening a practice in a big city means you will compete a lot for patients and then of course that's a lot harder. Up and coming smaller cities have the most promise for income. But it's always slow at first. I also got the advice from an OD that opening your practice in a smaller community gives you more variety to your job too. There aren't all the specialists that patients can see in a big city, so you see a lot more of everything rather than just doing refractions.
I don't really think you should make your decision about the profession from reading forums. These are a lot more likely to attract the extreme opinions - especially the negative ones that want an outlet for their frustrations. I'm not saying they are wrong to do that...they don't like the profession and they want to prevent the same thing from happening to someone else. But I imagine you can find plenty of MD's, dentists, teachers, lawyers, bankers, (you get the idea) who complain as much about their professions. If you shadow extensively, that will give you a much better perspective on the challenges to opening a practice (or whatever mode of practice interests you most - they all have pros and cons) and making a good income as well as the rewards that are definitely there too.