This is my favorite stapler, I have been using it for several years. First off, it is ergonomically designed: unlike my other (rarely used) all-angles stapler, this one is curved, made to fit nicely in the hand. I can use it for a long time and not end up with my hand aching. It does not require a lot of physical strength to staple through, either, unless you are stapling over 10 sheets of paper. The stapler will do as many as 20, but that takes stronger effort, of course.
Another thing I like about this stapler is that you can stand it up, on either end. This might not seem very important, but I do like saving space on my desk this way, and the stapler is easier to grab when it's standing.
Boston stapler is made of plastic and steel. It uses standard 1/4" staples which are very easy to load: the top of the stapler opens up, and you insert a full strip of staples. It also has an anti-jam mechanism.