Alpha 7 - Big Update!
Pre-release
Huge release!
Replay Support
You can open a previous session (if you have the "save to disk" option enabled), or an ACT log file. You can even force-enable overlays to see what they would have looked like. Note that currently, the replay mode does not have persistent settings.
CD Tracker
There are two CD overlays, one for personal and one for party. They have separate tabs to pick which cooldowns you want tracked in each one. The personal CD tracker will only track abilities/buffs cast by you, while the party version is filtered to party members.
It displays green for "Ready", red for recharging, or blue for active. When the buff is still active, the remaining duration is displayed.
Party overlay
There is also a party overlay. It is fairly incomplete, so it isn't quite ready to replace the in-game party UI.
When viewing a replay, it will even show unresolved damage as a red bar (seen here on the WAR).
Unfortunately, there isn't a rewind yet - the replay can only go forward, but it's a start. To advance through the replay, enter a number of events to replay at a time in the box at the top of the window, then click "Advance".
Overlay Management
Finally, there is an actual tab for managing overlays:
At the top, there are options are to show/hide all overlays, enter edit mode to allow you to drag overlays around (drag the border, not the contents, or mousewheel on the border to change scale), and adjust the opacity of each overlay.