I've been fiddling with this plugin for a while and am very happy with how its working for the most part. I have it set up somewhat like Movable Type in that all pages are fully cached and when one page is viewed it automatically caches the rest using the site map. This works really nicely as it ensures that the vast majority of people always encounter a cached page.
The only hole is that if I update or add a post or page (or do anything that affects menus, etc) I've got a load of cached pages that won't show my changes until the cache next expires after 3600 seconds or whatever. So my sidebar which lists the latest posts won't include the latest post on most pages, for example.
Is there any way to make it so W3 Total Cache empties its caches whenever things are saved in WordPress? So for example if a page or post is modified, a comment is left, etc it clears everything. Even better if there could be some kind of throttle (eg: if 20 people comment within a minute, it'll wait a minimum of a minute before trying to clear and subsequently repopulate the cache except for that one page).
If nothing like this exists it'd be a nice feature to investigate I think. :)