I really missed the global playback setting that Reaper has - as OP says was great for learning riffs, or slowing down to add a complex part and then speed back up, um, I hear that's what other guys do anyway...
It's all still possible in Studio One, but gets tricky if you have added different tempo's at different parts in your song - can't simply mess with the tempo at the bottom, but even here if you had all your tracks recorded with the original tempo info (this is a setting) and correctly matched to the correct kind of Timestretch (Gregor has a good video on this, but basically they map to: good for percussion, good for polyphonic sounds, good for monophonic sounds, and Tape style effects - i.e. the pitch will also alter) you can then use the tempo track at the top to globally alter everything - scroll to the start or end of your song and use the trim to move *all* the tempo points up or down. Should also be able to use for Varispeed type effects - e.g. speeding up and raising pitch of finished song (may need to change the timestretch type). Not as elegant as the Reaper/Logic solutions but seems to work well. Happy to be advised if there is a better way :) Putting here, since this question readily pops up in a search.