I'd like to start using them more and was wondering about their use in cold water (under 45 degrees). I normally don't begin using spinnerbaits until surface temps. reach that mark and just assume the Rig would not be very effective either.  Thoughts?

I find it to be the opposite, the rig works better in cold water and stops becoming effective once you get past prespawn. The same time you'd fish a jerkbait is when an A-rig is at it's best. 

Yep, As cold and nasty as you can stand to be out there seems best. I think we are about on the tail end of it around here now.