- full compatibility with the V2 module (max resolution supported, etc.)
- direct capture to buffer protocol objects (like numpy arrays)
- live manipulation of the framerate
- manual request of key-frames for H264 recording
This won't affect anybody doing basic stuff (capturing JPEGs, recording H264 video) but if you're doing anything like unencoded captures (YUV, RGB, etc.) or grabbing motion estimation data you will probably need to make sure you're running cutting edge firmware (sudo rpi-update) at least until certain firmware changes hit Raspbian stable...
Part of the reason this release has taken a long time is that behind the scenes I've been bugging the extremely long suffering 6by9 day and night with piles of requests for info about, or bug fixes to, the firmware. In the past, picamera has done certain truly horrid things to make things work smoothly on the surface. For example, if you requested an RGB capture from the still port, this wouldn't directly work: the still port would refuse to commit the RGB format. So instead picamera stuck the port in YUV format, attached a resizer with the same resolution as the camera (so it wasn't resizing), set *its* output to RGBA (not RGB ... because RGB didn't work on the resizer), performed the capture, then stripped off the redundant alpha bytes in Python. Ouch. Obviously this was horrid and slow. Well, no more! The still port in cutting edge firmwares will now commit an RGB format properly, and picamera will take advantage of that.
There's similar stories for unencoded captures on the video port. The upshot is that if you're doing stuff like unencoded captures or motion vector capture, you'll want cutting edge firmware (at least until it hits Raspbian stable, so if you're reading this a couple of months from now don't worry about it).
As always, PyPI packages are already up but Raspbian packages will take a few more days to hit the repos, so have some patience if you want to stick with the apt-get installation. I'm off to help out at picademy for the next couple of days, so I won't be able to answer questions until Wednesday. In the meantime, enjoy!