Developers will be able to download and flash the software to these phones to aid in the creation of apps using the preview SDK. The SDK, which is built atop of the latest Qt framework, comes with tutorials and design guidelines to ensure developers create beautiful, functional apps.
As for users who just wanna try out the new OS, it wont be much complicated except flashing a new file as a regular ROM.
Canonical makes no mistakes when providing a disclaimer that this wont be the final piece of code and therefore it could be unfit to run it as a daily driver.