Josh, I use the transpose somewhat regularly. I know you could do the same by moving notes up and down in piano roll, but i use it to check if synths or keys sit better in the mix an octave or two either side of where i write them. I've also used it to try other interval transpositions to check potential harmonies.
I've also had a bit of dumb luck with the arpeggiator, but i don't use it much.
I typically load synths in as midi source and audio tracks for the vst fx versatility.