I found that having Residuum (or, as my players started calling it, Pixie Dust) around in small quantities as a currency worked well once my players hit Paragon and started leaving the Material plane.

For example, if you wanted to buy a magical sword off of an Lawful Good angel, would you pay him in gold? Heck no! That angel is from Celestia, they use gold to build homes and paving stones, it's basically worthless. Residuum, on the other hand, has value no matter where you are.