Unless you're fishing for what would traditionally be considered big game species, you should be using tippet rings. It doesn't matter whether you're fishing machine-made extruded leaders, furled leaders or hand tie your own. Tippet rings have their place in all of these scenarios.
In an earlier featured entitled Tip: Stop Wasting Money on Leaders, we detailed how we feel machine-made tapered leaders are one of the biggest money pits a fly fisherman encounters. Adding tippet rings to the tips found in that article take the whole picture to the next level of practicality and good sense.