Hmm, your're right Dean it might be a problem in some cases though I think you would see your forum post because its on a different page, ForumThreadView.aspx, but the page that holds the forum module might not show your response right away as far as the most recent post info.
Looks like there is a sqldependency that can be used
Not sure if we can make that work with other dbs, my guess is not.
Maybe we should focus on caching of modules instead of at the page level. There actually is already a cache duration setting in module settings but I haven't reallt done any measuring of its benefits and its set to 0 by default which is no cache at all.
Would be good to get some measurements on that. We could leave it at 0 for forum module.
So, kwa, for example, you could put an html module, blog etc on a page and set them to have a cache time > 0 and see what the load tester has to tell us.