Does anyone know if this includes AAC fixes? It's pretty hefty weighing in at 51.4MB.

7.1 seems to be only available on Mac so far. The Win version is still 7.0

//EDIT...

I stand corrected it is 7.1, give me a minute and I'll encode some AAC's...

any sign of AAC+ playback?

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nope.

What's New in QuickTime 7.1
QuickTime 7.1 delivers numerous important bug fixes and addresses critical security issues. This update is highly recommended for all QuickTime 7 users.

New in QuickTime 7 Player
QuickTime Player provides many exciting features.

• H.264 video support. Watch movies created with this state-of-the-art, standards-based codec which delivers exceptional-quality video at the lowest data rate possible.
• Live resize. Playback continues smoothly as you change the size of the QuickTime Player window.
• Zero-configuration streaming. Now QuickTime automatically determines the best Internet connection speed for your computer and adjusts it as necessary. And if a connection is lost during streaming, QuickTime automatically reconnects to the server.
• Surround sound. QuickTime Player can now play up to 24 channels of audio. With QuickTime 7, your PC, and surround speakers, you can enjoy the full effect of your surround sound movie or game.
• New and improved playback controls. Use new playback controls to adjust settings for the best viewing experience. Easily change settings including jog shuttle, playback speed, bass, treble, and balance.
• All-new content guide. The new QuickTime Content Guide provides access to the latest in entertainment on the Internet.

New in QuickTime 7 Pro
QuickTime 7 Pro users enjoy not only all the great features in QuickTime Player, but also the following new QuickTime Pro capabilities:

• Create H.264 video. Create incredible-looking video for any use, from 3G (for mobile devices) to HD (high definition) and everything in between.
• Record audio. Capture audio for easy podcast creation or slideshow narration.
• Create video for iPod. QuickTime Pro allows you to easily convert your existing movie collection or video podcast into a format that can be played back on iPod.
• Create surround audio. Create a rich multimedia experience by adding multichannel audio to your movie. QuickTime automatically mixes the audio to work with the speaker setup of each user.
• Floating controls. Easily access functions like pause, play, fast-forward, and rewind while watching full-screen movies.
• Improved movie authoring. Editing tasks are much easier with new hot keys for in and out points. In addition, Movie Properties has been completely redesigned to facilitate simple and efficient movie authoring.
• AAC constant-quality mode. In addition to the existing constant bit rate mode, QuickTime 7 Pro allows you to create AAC audio files optimized for constant quality for a consistently high-quality listening experience.
• 3G streaming. Create 3G files for RTSP streaming that are interoperable with 3G streaming handsets and delivery architectures.
• Automate with VB Script. Automate your QuickTime workflow with native VB Script support in QuickTime 7. Developers can also use VB Script to access the new QuickTime Active X control for creating custom multimedia applications.

A few things have been changed around quicktime, UI wise, but no idea about codecs

For people who do not need/want to install iTunes, there is a standalone version as well.

Edit:
Just noticed that Quicktime Alternative was updated.