Is it possible to alter the playback *preview* speed? Is it possible to change the speed of Premiere's playback of the video without altering the speed of the produced version? Even if I could play it only 1.5x faster, it would mean a lot of time saved in the long run.
Yes - while playing the video, press the L key to increase playback speed and press the J key to decrease it.

For further options, please reference the relevant Premiere Pro documentation.