This is especially true with wines like Aussie Shiraz or big California Cabs because of their monstrous tannin structure that often times needs to be substantially aerated. However, today I tasted the a Pinot Noir that I reviewed yesterday (2006 Firesteed Pinot Noir) and noticed that it had improved at least two points from the day before. It was softer, more complex, and finished with much more polish than the day previous.
I'm convinced that before giving a 100% assessment of any wine, that it's vitally important to save a glass until the following day when it can be analyzed again. I would be interested in the opinions of those who have experienced this second-day improvement as I have and those that think I'm just nuts too!!