My experience was essentially the same, and I found that nothing satisfied both purposes. Snow pants are a lot like rain pants, and you don't hike in rain pants unless you have to because they don't breathe very well. Unzipping them works, but snow pants are still going to be way overkill for spring, summer, and fall hiking.
My happy medium came from getting a pair of quick-drying, highly breathable backpacking pants (I settled on the Mountain Hardwear Mesa). Then, in the winter, I wear a 4-part system. Starting skin out, I wear Under Armour, heavyweight Merino Wool, the MH Mesa pants, and then some half-zip rain pants (GoLite Paclite). With this system, I stay bone dry, I can vent, and I'm warm enough hiking at 0º.
My experience was to sacrifice the snow pants for 3-season hiking stuff and then use it modularly. This was after failing to find a layer that satisfied both, truly. I hope someone here can help you find the perfect piece, but it is not a crime to have awesome, comfortable, and bombproof snowpants and then spend another 50 bucks on some summer hiking trousers. I give the MH Mesa pants 4.5/5, since they get a little static.