Besides the native 64-bit support to Flash 11, there's also Stage3D API support (for delivering 3D support via Flash), G.711 audio compression support for telephony applications, H.264/AVC software encoding support, JPEG-XR support, and socket progress events. The Flash 11 Linux binary also now has vector printing support to match the Windows and Mac OS X capabilities. Details on the various Flash 11 features can be found via this Adobe.com page.
As far as what's new to beta two, early testing and the feedback of Phoronix readers has just yielded the Linux binary at least is a lot faster and more stable than last month's beta. Unfortunately, there still isn't yet any VA-API acceleration support to Flash 11 on Linux for GPU-based video playback acceleration support on more hardware, but for now it's still limited to NVIDIA VDPAU and Broadcom Crystal HD.
The latest 32-bit and 64-bit Flash Player releases for all supported platforms can be downloaded from Adobe Labs.
If you missed it, recently on Phoronix there were Flash 11 power consumption tests. Expect more benchmarks upon Adobe's official release of Flash Player 11 for Linux.