Before I did hacker school, I thought I was a good programmer. But being in a room with 20 incredibly smart people really makes you realize what you don't know. Since joining, I've:
-Authored a (now-committed) patch to the python core
-Written a SPDY implementation
-Contributed to many open source projects
-Learned C and Rust
In short: If you have any interest, even if you've only done a bit of programming before, apply. They select on passion for self improvement, not skill.
EDIT: I'm not too comfortable singling out the skillsets I'd qualify as 'least experienced'. Suffice it to say there are people who do not come from professional programming backgrounds who have picked up enough to write up fizzbuzz, and speak intelligently about the things they've used in the past, and would like to work on in the future.
For more on what people are actually working on, take a look at Hacker Schooler Brendan Nee's web app: http://hs.bn.ee/
Or come to the excellent Hack & Tell NYC meetup and you might find one of us there presenting, as we (well, not me) did this week.
Seriously though, it sounds awesome. My CS skills are up to scratch but I'm still a pretty young programmer so I hope I can keep up (assuming I get in).
I managed to continue working at diminished capacity for Bug Labs, and it was a LOT of work to manage both, but it's really worth it.
If I had more funds to sustain myself I'd try to do a batch at Hacker School and then a session at Founder Institute and go into full-time entrepreneurship really well prepared.
But I either need a situation where I can work 20 hours a week to pay the bills or I need to start taking out of the pot I'm saving for starting a business. We'll see what happens.
I was accepted for batch[3] in early Feb and planned on quitting my game industry job and moving to NYC this summer, but a month ago I got an offer from an awesome YCS11 company and ended up moving to SF instead. Best wishes to everyone who ends up going, it's a shame I won't be able to hack with you all. :)
Edit: ninja
To those that feel they don't have enough experience for HackerSchool, or are just starting out in programming, or looking to start out in programming, I could highly recommend http://devbootcamp.com/. We're closing applications shortly for the Summer (June 11th onwards) cohort.
I'd be happy to answer any questions here or via email (lachy@devbootcamp.com)