well the stock z breaks are more than adequit for everyday driving and light autox/track. But if u want the best out of the car in terms of breaks, rear calipers and front upgrades are the way to go.
some good things come to mind to upgrade would be easier to service, marginal performance gain, more choice in performance pads, and just looks nicer.
cons, cant really thing of any? just u'll get ur hands dirty and have to source the parts. for me, bleeding the calipers were a pain because i used 85 maxima calipers and the way it sits, the nipple was not facing 12noon so some air was still getting trapped inside. took me 2 weeks to figure out the problem. Now i have to bleed it while 1 side of the caliper is loosened and tilted up. No biggie but still a pain.