I'm 200lbs (brakes are more important when you're slowing more mass) and ride year round on rim brakes (cantilevers on my summer bike and V-brakes on my winter bike). I've ridden several disc brake equipped bikes. Properly setup they are very good when it's dry, OK when it's rainy, barely tolerable when it's muddy/rainy, and poor in cold/wet/snowy conditions.
The main benefits to hydraulic disc brakes are that once you get them setup they require very few adjustments, they offer similar stopping power no matter what the conditions, they don't grind away at your rim, and brake modulation is much better.
Unless you're doing a lot of unpaved stuff or a lot of snowy riding I'd say that you don't really need them.