On products prior to Sonar there was a quick tool that allowed you to click to cut the tempo in half, keep it normal or double it.  It was usually right next to the current tempo display and had a metronome icon with 1, 2 and 3.  This was VERY convenient if I need to record a very fast bit that I'm not able to execute cleanly at normal tempo.  Temporarily cutting it in half made it easy to record the bit then switch it back to normal.  I can't find anything like that in Sonar.

I believe the Tempo Ratio function went away with X1. It wasn't very useful in most instances because it could only be used with pure MIDI projects using direct-monitored hardware synths; having any audio tracks (including soft synth outputs) in the project disabled them.

The functions are still exposed in keyboard shortcuts but I lack the hardware to test them.