To a CO elite, using milages to upgrade in domestic flights is definitely "wasteful". CO will upgrade their elites free (based on availability)
For international flights, I rather buy a ticket and use milages to upgrade. You can get a LAX - London ticket around $500.00 and burn 50,000 miles upgrade to CO BusinessFirst which normally costs $5,000. That's 50,000 miles for $4,500.00 rather than a free coach ticket (which is only $500.00).