A few years ago we had a retired machinist mentor our team and he put me on to TCGT inserts:
http://www.kbctools.com/can/Navigati...fm?PDFPage=251
They work very well for aluminum and plastic.
For steel we use a more robust insert like TNMG:
http://www.kbctools.com/can/Navigati...fm?PDFPage=260
The triangular inserts work well for general purpose turning and facing. We already had the toolholders, so we stuck with that geometry.
For retaining ring grooves we use the Nikcole mini system:
http://www.kbctools.com/can/Navigati...fm?PDFPage=330
Another thing to consider is a quick change tool post:
http://www.kbctools.com/can/Navigati...fm?PDFPage=486
We installed one of these a couple years ago, and it has dramatically improved the efficiency of our lathe.