I was actually going to suggest this exact method of archiving. Glad you anticipated it. Needless to say, I approve.
1. File collisions could be avoided if the filename included the time as well as date. However, I find ,  to be personally acceptable.
2. Right-click option to Archive current log = good thing.
3. An advantage to using current.anu is that when the viewer is invoked, it can easily be programmed to display the most current logfile. Obviously, it should not lock this file when it is being viewed.
4. I see the viewer as a separate .exe from Anuran. From the limited comments in this thread, there are some who want one, some who don't, so a separate viewer would please both crowds.
If you don't mind another of my drawings, here's another mockup of a simpler two-pane viewer layout. (Stick with whatever you feel works best, however):
0. Proposed viewer names: Anuview, Anuvu, Anuran Viewer
1. The panes and window itself would be resizable, of course.
2. The items in the logfile pane would be organized according to file datestamp, or according to the first datestamp contained within the file itself, in case the file properties get messed up by Windows.
3. On startup, Anuview defaults to current.anu. Logfile pane defaults to \archive, but the current.anu is always displayed on top.
4. If Anuview is started by double-clicking on a .anu file, it displays the file, regardless of where it is, plus any other .anu files that are in the same directory as the .anu file it is displaying. This is for folks who end up moving their logfiles around.
5. Do we want a full-on file tree in the logfile pane, or just a 'flat' list of logfiles in \archive?
6. Ignore the titlebar and status bar ornamentation, they come from bblean's skinning engine.
7. And yes, I basically took a screenshot of MiniAim, and cut and pasted around.
1. If you apply a 'tail' function to the viewer, it could even auto-update the contents, which provides a fingertip-ready view of the last x hours of entries. I worry a little about people who want to tail their own personal log, but it does provide a quick answer to the question "Now, just what the hell have I been doing the last hour?"
2. An automatic vertical timescale that visually measured the time between each entry would still be a pretty neat Stupid Coding Trick.