my current bike is stone stock, for now. I may upgrade the brakes from tektro to apex just to match the rest of my components, but, not because of anything performance related. probably much cheaper to get better pads and call it a day, but, oh well, purely aesthetic and a bit of an OCD thing.

edit - I'll probably upgrade the saddle over winter and try a few. only complaint i have on my bike and its a minor one.