Pros
You get to work outside in beautiful locations and complete a variety of different projects. Housing is provided, and the crew begins to feel like family very quickly. It's great to be around like-minded people in a fun environment. Lots of opportunity to develop professional and personal skills. If you're interested in doing this kind of work for a career absolutely do ACE
Cons
All the pros can also be all the cons depending on what type of person you are. Working outside, meeting lots of new people, camping for 8 days at a time - all of that can be wonderful and difficult. The biggest con in my experience was the turnover. If you're planning on doing a term longer than 6 months, you'll see lots of friends come and go and for me that became pretty draining towards the end. Also, it can take a long time to actually start. It seemed pretty common to have a start date scheduled months after your interview.