The Black Diamond Alpine Bod fits a wide variety of leg sizes and waist combos. The leg loops are highly adjustable and, more importantly, they are quick to adjust. Mountaineers love this climbing harness because you can put it on very quickly without having to step your boots and crampons through leg loops. If you are teaching a big class of new climbers, this harness is easy to fit to someone quickly. Also, the harness is relatively compact. Climbing gyms love these harnesses because they can be thrown in one bin where they take up relatively little space. Lastly, they are time-tested and bomber. It is hard to wear them out; just about every piece of webbing is beefy. This harness even comes with gear loops and a haul loop that make it suitable for multi-pitch climbs.
The main dislike with this climbing harness is its groin comfort. The leg loops pull into the groin (most leg loops that mostly apply pressure to the legs). This is not a big deal if it is your first time climbing and you are just doing a couple of routes. But if you are going to climb a lot you will want to upgrade quickly to a more comfortable harness.
The Black Diamond Alpine Bod harness is lighter than the regular Bod but is still heavier than most other light harnesses. This is due to the really big buckle and thick webbing. Unlike most harnesses, there is no self-locking buckle, so you need to double back the harness. This makes putting on the harness take longer and is one more safety check you need to make, especially if you are teaching lots of students. Also, it means that if a harness is a little too small and there is not enough extra webbing you need to take off the harness and find a bigger size. This can be annoying if you are teaching a big group. It is a problem solved with other harnesses such as the Black Diamond Momentum DS or Petzl Corax where one size fits more people. This harness does not have a belay loop, which means the webbing near the groin often dangles (this is annoying when walking around a lot). The solution some people use is to clip a carabiner or locking carabiner to connect the waist and leg loop.
This harness is designed for mountaineering and glacier travel.
This is the least expensive harness there is. It is burly and will last forever. If you are just doing a mountaineering route or two, then this will work for you.