Attended a bootcamp (General Assembly) in 2014. Very positive outcome for me I got a job offer the week I graduated, but like others have mentioned, a significant number of others had a harder time getting their first gig. Some gave up and I don't blame them. I'm in San Francisco where competition and opportunity are very high.
Bootcamps have their flaws, but are definitely filling a need in the tech sector. There's too many dev jobs and not enough devs so while there's some saturation leaking from bootcamps, it's not because there aren't enough jobs; it's just very competitive and companies generally do poorly at recruiting. Bootcamps are trying to fill a void, but they're not all equal.
For anyone thinking of attending a camp: look for camps that offer scholarships to attend. They're hungry for students for a lot of reasons but also it's indicative of a camp that really wants to offer you something and they've managed to get the big companies to pay the way for you. Yes that's how many of those scholarships work. The bootcamp networks with big companies like Google who offer sponsorship for a set amount of students (usually minority students). Whatever you think of the camp, that's a good sign they're trying to expand their offerings and those camps will usually do a great job of helping you succeed.
Second, look at the more established camps. If you're a woman, Hack Bright and Grace Hopper and the like are premiere camps. Their programs are amazing. If you can get to one, consider those your best options for getting a quality education. For others, App Academy has a well earned reputation; Hack Reactor is competitive; General Assembly is well established and has vast resources for students. I'd say Dev Bootcamp but as someone else mentioned, they've changed somewhat over the years and I'm not sure where the quality lies there. I work with a lot of bootcamp grads from different camps for the past few years and I continue to mentor at these camps so this is my firsthand experience with them.
Finally, be ready to study ...not necessarily all day everyday (people have families to attend to) but definitely for a solid 8-10 hours to get the most of it (and try to take 1 or 2 days off; the brain needs a break to absorb all the things you learn and it will be tempting to keep going without breaks).
In all cases, you're going to be surrounded by other students and developers of varying experience daily ...this is the greatest benefit you reap from bootcamps. You have people you can go to hourly! Ask anyone who is self taught how valuable it is to have this sort of access to getting your questions answered all day every day. You're also going to be at a place that constantly networks with companies on your behalf. Regardless of how good the camp is at placing grads, the fact is they're already in the door and it's a leg up for you to have them do a lot of foot work to connect you. That brings me to networking: bootcamps are a great place to do it. There will be guest speakers and events to attend every week and professionals on site whose daily job is to talk to companies so that you know what they want to hear.
Whatever you think of bootcamps, they're always a hotbed for networking and learning. If you go into it with goals, a learning mindset and dedicate your mental resources for the 12 - 24 weeks you're there, you'll do well.
I must emphasize to make sure you set your goals before hand and chase them tenaciously. I think one of the best I things I did was have a mental timeline and SEVERAL acceptable outcomes that I'd be satisfied with. For example, my endgame was to get a job as a developer within 3 months of graduating. During that time I'd attend weekly workshops and network; and I set a schedule to study algorithms and build an app everyday in any language (the idea was repetition, make hacking second nature while studying algorithms was more about digging deep). I would have accepted working as a contractor, creating my own business or being employed as a junior dev and my study schedule made all of those equally likely outcomes. I focused on improving myself, establishing my own network and at the end of 3 months I'd be prepared to either strike out on my own or have a job. Two of those were in my control, and that was important. Nothing can be promised in a bootcamp no matter where you go so it's important to set realistic expectations and to hold yourself accountable for the outcome.
It's a lot of hardwork, but I found it enjoyable, productive, efficient and just flat out fun (really enjoyed late nights with other poor students and all the creative ways we found to grow together) and I highly recommend it.