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.
If you're not familiar with them, tippet rings are tiny metal rings (typically made of nickel alloy) that are intended to be tied at the terminal end of your leader. Instead of attaching tippet material directly to the body of the leader, the tippet ring serves as the junction between your tippet material and your leader. Because of their tiny size (2mm and 3mm diameter are most common) and nickel alloy construction, tippet rings float, making them viable for fishing nymphs and dries. Concerns about strength should be set aside, as tippet rings are rated at 25-30 lbs.
As mentioned above, tippet rings aren't reserved for folks that are tying their own leaders by hand. In fact, they serve to make the biggest impact for those of you that are still paying up to $10 per fluorocarbon leader. Instead of chopping that leader up and quickly needing to buy a new one, you can modify your store-bought leader with a tippet ring and make it last you a year or more. Typically, you'll want to cut off around 24 inches from the end of your extruded leader. Attach a tippet ring to the resulting end using a simple improved clinch knot (or the knot of your choice), and off you go.
Fishermen that are introduced to tippet rings often initially worry about leader/fly turnover and drag, but these concerns have largely been set aside. Tippet rings turn over flies just as well as a leader with a direct line-to-line connection and drag worries, which are most likely not a concern anyway, can be resolved by placing a dab of floatant on the tippet ring to keep it riding high in the water. If folks like Gary Borger and Lefty Kreh are comfortable using them, so should you be.