I see a lot of people don't recommend it, but here's my experience so far.

 I just started a couple of months ago and my foreman is fantastic. Really cares about the projects and it shows. He used to be a carpentry teacher at one of the local tech schools and has years of experience building. Most of the volunteers have been with Habitat for years, quite few over a decade, so they are a wealth of knowledge as well. My first day they put me on shingles, I swing a mean hammer and I'm not afraid of heights, so my second time I was on up staging shingling under the roof and the third time the foreman just gave me a wall to myself - so I did all my lines and strapping by myself. He explained how I can do it alone, checked on me a few times, and as there were no problems with my measurements and work, left me to my devices.

 In the meantime I went to a local tech school for an adult carpentry class. That's kind of an overstatement. It was six sessions of working in the shop making an Adirondack chair. The point is, I got to use a bunch of saws and tools.

 After shingling was done, we started floooring. But now that I knew how to use all sorts of saws, they trusted me to be the cut-lady. I cut all the pieces for the floor and my measurements were impeccable. I also did drywall one time at a different site and last time I was on insulation and had a blast: cutting insulation  pieces on the table saw and filling the cracks with great stuff pro.

 The bottom line is, I guess it depends on the people you work with and how invested you are. My foreman is amazing in that he wants people to know what they are doing and how to do it properly. I told him I want to learn and he sees that, so he's willing to teach me. 

 Also, there are four projects in my area, so every once in a while I go to a different site at a different stage of building and do new things. The closest is an hour away, but I'll be damned if it isn't the best part of my weekend.

 I honestly can't recommend it enough. It's been a great experience for me, I've learned a ton, I've met some wonderful people and it's definitely something I'll continue doing. 

The only thing I could do without personally is devotion, it's a religious organization, but I knew that going in and I respect the people, so I just sit quietly and sip on my coffee.