The GT Academy 2011 functionality prepares the game for this year's tournament, the goal of which is ultimately to turn a fan into a real race car driver. You need to be aged 18 or older, a European resident, and perhaps a little crazy. This is similar to the US tournament that began in December.
Friend Rankings add the oft-requested friend leaderboard functionality, making it easier to brag. The update also included a few bug fixes, including adjustments to performance point calculation and car trading.
Previous updates include upgraded server infrastructure, mechanical damage in online races, seasonal events, an online dealership, various tweaks, the addition of the performance points system, remote races, course maker adjustments, and more.
You can say a lot about GT5, and we have, but you can't say it lacks for updates.