Skypimp,
I am right in your boat of working toward the single engine commercial with about 200 hours. I have had 2 encounters with rime ice and although they didn't in any way degrade performance, it scared the heck out of me. I agree with flyandive, in that you should never base your decision based on PIREPS and published AIRMETS etc. Flight plan for yourself and when it comes to instrument flying and flying through visible moisture you really need to exercise sound judgment. If in your flight planning you determine that the freezing level lies at X altitude and there is a cloud layer at that altitude then it's probably not a good idea to fly through it in a Skyhawk. I did fly a high performance aircraft through such a layer and was able to get on top soon and break out. We still accumulated some rime ice, but I was with a highly experienced instructor/airline pilot who instantly told me the dangers of icing and how he never messes around with even a little bit of ice. Because it was a high performance airplane and he knew darn well he could break out soon, he made the decision to fly through the layer. I think it all boils down to experience and good judgment. Good luck and fly safe.