Minecraft Update, change logs

The full changelog is listed on Mojang's website (copied below).

The line you mention, "Added a few other things for players to discover," is in the Tutorial World section. Therefore I suspect it just means they added some cool touches to the tutorial world to demonstrate the use of new items (pistons, stacked fences, etc), to add to its charm. They may have added some little easter eggs to this world too, but I can't say for sure.

Minecraft: XBox 360 Edition July 2012 Update Changelog: http://www.mojang.com/2012/07/minecraft-xbox-360-edition-update-is-out/

Features:

• Added Pistons & Sticky Pistons.
• Added Stackable fences.
• Added Shears – required to get wool from sheep, and to collect leaf blocks.
• TNT needs Flint and Steel or Redstone to detonate.
• Redstone wire will now connect to a repeater.
• New textures for Cobblestone and Brick.
• Added Character Skin Selector to allow players to choose their skin from the default skins, or from Downloadable Content skin packs.
• Added lighting improvements (brought forward from 1.8.2 update) and snow & rain improvements.
• Added a save file cache to improve the speed of displaying the saves list.
• Added ban list functionality to allow players to self-ban from levels they feel contain offensive content.
• Added a ban list section to the How To Play menus.
• Added an option for the host to limit online games to only players in their friends list (no friends of friends).
• Added a seed display to the level load screen (requires existing levels to be saved out again to add the display).
• Changed the tooltip display setting to in-game tooltip display, so that tooltips always display in menus.
• Added the crosshair to the list of things affected by the opacity slider.
• On using the quickselect bar, the opacity of the quickselect, tooltips, splitscreen gamertag display, and crosshair will be set to 80, and will fade back down to the user opacity setting after 6 seconds of no quickselect bar use.
• Added some more Tips & Trivia to the loading/saving screen display.

Tutorial World changes & additions:

• Added optional tutorial for Pistons and Redstone.
• Added a self-building bridge to the castle using Pistons.
• Added some sugar cane, cactii and clay to the world.
• Added a few other things for players to discover.

Fixes:

• Fix for only the host being shown the pop-up when any player attempts to place lava near the spawn point.
• Fixed tooltip for Flint and Steel.
• Fix for Note blocks not showing notes.
• Fix for Leaderboard reads taking too long.
• Fix to block players re-entering a level they have been kicked from, until the level is restarted.
• Fix to stop players being able to join a game when they are not a friend of any player in the game.
• Fix for Netherracks re-appearing after being mined.
• Fix for a rare crash on entering the Nether.
• Fix for attacking enemies at a different level not damaging them.
• Fixed a problem causing some save games not to load.
• Removed Herobrine.

It is possible to delete the update, however this will delete all updates to all games, and can therefore can be fairly dangerous and is not recommended. Even after doing so, you will still be unable to use your world, unless it has only been played on Minecraft version 1.0.0 (ie you've never updated Minecraft previously). Also, you will be unable to play on Xbox Live until you update.

To delete ALL game updates (again, not recommended):

Settings > System > Storage > [Hover over Hard Drive] > Press Y > Clear system Cache

If you choose to try this, keep in mind that you will be unable to play on Xbox Live until you perform the update again.