I always find that rim brake pads get trashed pretty quick in rain and snow. I love the mechanical discs on my fancy tourer, but that's way too fancy for bad weather riding. Personally my usual bad-weather bikes are fixed gear beaters- stops well and reliably, you know quicker when you're slipping, very little to maintain/wear out. This year is going to be interesting because I got an old single speed hardtail mountain bike with a disc in the front and a v-brake in back that I'm also changing to fixed (I used to have to deal with skinny slick tires because I had 650c. It's doable, just a little more difficult).

Commuting and market-cruising is pretty important transportation. You know your own budget, but I'd give it a little more credit. I recently helped my cousin find a new commuting bike- he commutes 4-5 days every week, all year in a place that snows, and his attitude was still "I don't want to spend too much on a toy". It's how you get to work most of the time! It's not a toy anymore, it's one of your main vehicles! Once you start to add up how expensive it is to operate your car, time spent digging it out and paying for parking, maybe the cost of the odd fender bender from sliding around a 2 ton speeding box on ice, you'll probably more than make up the cost of a decent, reliable bike.