RE: Faster gameplay
Shading something (command range, reachable hexes and so on) causes delays during movement, highlighting usually doesn't. I tend to play with reachable hexes on, and the delays when zoomed out or zoomed in are significant. At "normal" zoom levels, there is usually no delay.
The tip about fast-forwarding the replay and maintaining the increased speed is good. There are disadvantages, such as not being able to see the results of plotted artillery/air strikes that occur at the start of a turn (FWWC, Panzer Battles) at higher speeds, but it works well.
Sometimes I watch the replay twice, the first time fast-forwarded at several times normal speed and the second time fast-forwarded until near the end of the replay when I switch to normal speed and then slightly fast-forwarded speed.