i'm extremely fond of bullpups. my PS90 is a stellar rifle. absolutely outstanding. ergonomics are very good. you do have to come off of the gun to do a mag change, but it's not nearly as annoying as the AUG, and you get a 50 rnd magazine, given that it's not a battle-rifle, it's not likely you'll ever NEED to.
many of the 50bmg single-shot and bolt-action guns are bullpup. e.g. barrett's m82a2
there are some good 22lr rifles that are bullpup. e.g. walther G22
the primary advantage is that it's a far more compact package than you'll ever get with a traditional configuration, and yet, you can still have a rifle-length barrel instead of a carbine-length or 'shorty'