Honestly, you can do anything on a Banshee you can do on a ex, or a Z, the only difference is you have to plan ahead or pick your mods cautiously and after researching them. If you just go out and throw the first set of pipes, or ones you like because of the name, then you might be working against your overall riding style. For instance, you trail ride, but like the sound of the CPIs, well it's not gonna be as fun to trail with a set of CPIs as compared to a set of Fatties. Just plan ahead how you intend to ride it, and it's okay to say everything, just be sure to do mods that help "everything", like Fatty pipes enhance the overall powerband, not just low or high rpms.
Reliability is the same as any other, they don't need a lot of maintenance, but with a little (same as any machine, oil, clean, grease, inspect) it'll last a long long time, just make sure your jetting is right after mods (which is also the same with any machine). If your buying used, be extra cautious to buy one that hasn't been dogged and not maintained or you could be asking for trouble, this is also true with all machines. There's nothing worse than to buy someone else's problem and we've all done it.
Mine's an '02 and has been ridden pretty hard, cleaned pretty well, and correctly maintained. I can go out at any given time, kick it once or twice and count on it to do whatever I ask with ZERO problems, and it has for well over a year and a half without one stutter. I may have fouled one plug in all that time. I just raced a cross country race this weekend with my banshee (which is "typically" not it's field of expertise) and I have a lot of mods that promote the low and mid ranges and my lap times were all within range of the others, so the banshee can do it all if you just choose wisely.