Yesterday I ran into a little problem logging into Drupal. Weird thing was that it worked fine under Firefox but IE and Chrome were both failing to log in. There were some suggestions that it could be cookie related, but I cleared my cookies and that didn't seem to do the trick, nor clearing cache, and a restart of my machine (as silly as that seemed) didn't seem to work either.
As usual, the truth is much simpler: I should have noticed when I started getting random SSL certificate expiration notices that talked of certificates being expired, yet the expire date on the cert was 7/23/2011. (On a Google tool no less).
So, long story short, after a half an hour, I took a look in the lower right hand question and saw that the time had been set to the future and it was causing cookies to expire too soon - set my time back and everything looked good.
I'm not familiar with Aegir and this is a complicated issue, I was thinking about more granularly (is that a word) deploying modules using cvs and this technique which is a little more lightweight (and probably cheaper), but I could see where the other approach would have it's strengths.
As with any technology or process choice, there are pros and cons to each.
Clearly, again, the one take away from all of this is that drush is awesome.