Whilst sorting our my wallet yesterday I came across a few posts that mentioned that "-rescan" is not necessary anymore (since 0.7.(?)), as the client does it automatically at start-up.
This is not correct (although perhaps the other posts were talking about a specific context that the "rescan" option is no longer necessary).
Doing a "rescan" is not a trivial operation (before upgrading to 0.8 on my laptop it would take well over 15 minutes to perform).