The pros of being a host family are the incredible students. We were sent a very long list of possible students, including summaries and introductions written by the students themselves. We were allowed to choose students who would be a good fit for our family based on their interests, personality, etc. so in that sense, our experience has been wonderful.
The difficulty for us is the very tedious, redundant, unnecessary amount of contact we're required to have with the volunteers. I'm in favor of strict background checks as well as regular contact, and getting the international students together for activities. All that is great. However, the volunteers and liaisons tend to make every "mandatory" activity three times as long as it needs to be, with no real purpose. Every part of training seems to be repeated 3-4 times and if you are a busy family trying to juggle bio kids, an international kid, school, and bringing your student to cultural and tourist attractions, it's easy to get frustrated by the endless, repetitive, lengthy contacts from the various volunteers.
If you're perhaps a part time or stay at home/homeschool family, or looking for a social outlet in addition to hosting, this would be a good fit. If you're a student, I'd look carefully at the family and make sure it's a fit for you as far as you can tell, ahead of time. You're allowed and encouraged to have contact before you arrive, so that's a good time to ensure it will be the experience you hope for. It's also really expensive and they expect students to pay for additional items once they're here, so check into what program will give you the most for your $.