Both questions are great and actually depend on the type of “image” chosen. With Yocto, we can easily generate multiple OS images for the same distribution. Typically, we have a “development image” with all the tools pre-installed and a “production image” which is optimized for size, boot-time and NAND corruption safety.
For the Raspberry Pi 3 we are currently testing and we’ll release initially only a development image but the tools for generating a production image will be there and available to anyone.
Regarding the boot time:
on other ARM boards, we are able to go from power to first sound in around 3 seconds. On the Raspberry it will probably always be a couple of seconds slower due to their weird boot process through the GPU firmware but I see possible to stay at aroud 5-6 seconds there, too.
And about SD card corruption:
this will already be available even for development image on the RPi3 and we are testing it right now. The filesystem is mounted read-only, so you can safely turn off the power at any moment without risk of corruption. There is a separate partition mounted in R/W for keeping user data and that is saved between updates. The golden rule is that whoever writes to that partition (e.g. configuration data for a plugin) should keep in mind that files could get corrupted and act accordingly.