According to issa3032: Install the optional Firmware 2.43 update, and the system actually seems more resposive. Anyway, I booted up Gran Turismo 5 and was browsing around the options when I noticed something interesting: When you uncheck the "Disable Advanced Downloading" it asks you to "accept" or "decline".
In the past you used to get a warning message saying this feature would be enabled in a future firmware update. Well this message no longer pops up. I guess now we know what the firmware update did in addition to speeding up the XMB.
Note to others: "Unlike previous updates, firmware v2.43 is specific to the Japan region, and only PS3 users there will be required to install the update."