Fleece is not a softshell, although a softshell may be fleece-lined. Softshells are usually thicker than hardshell and feel kindof like thin neoprene, although I'm not sure what they are made of. The thickness gives them better insulating properties than a hardshell but they breathe much better than hardshell. They are pretty good at cutting wind and are water resistant, so they are great in a light snow or rain. If the wind kicks up or it starts snowing hard or raining or sleeting, you need a hardshell to keep you dry. In something like heavy sleet, softshell products will wet out pretty quickly. IMO, new products like eVent are blurring the lines between softshell and hardshell.
I was out XC skiing yesterday in the Uintahs. Temps were in the teens and I was wearing a thin base layer, a poly top, and softshell on top of that. I also have softshell pants that are perfect for these conditions. When we got to climbing a bit, that was even too much since the sun was out, so I stripped off the poly top. The previous night, it was lightly snowing, and a base layer, thin fleece, and softshell were perfect for me. Just like Steve said, you really need to try a bunch of things out and see what works for you. I personally generate quite a bit of heat under activity, but as soon as I stop, I cool down really quick, so in extreme conditions, I carry lots of layers. The worst is ice climbing when temps are below 0, where I need just a base layer and maybe a shell if it is wet while climbing. Then when belaying, I have to add fleece and a giant down jacket just to stay warm.
What a fantastic weekend it has been to get out! Couldn't ask for better conditions!