After launching the Android Marshmallow alongside the Nexus series of smartphones and the Pixel C Tab, Google has now released the factory images for a range of Nexus devices.
Essentially a factory image is an beta version of the ROM that you can flash onto your device manually. Yes, you won't be getting an OTA update as of now. But Google has promised to push an OTA update soon enough.
However one will need to wait for a month or so to get the OTA update of the Marshmallow onto their devices.
The range of devices supporting the Marshmallow OTA update include the Nexus 6, Nexus 9 WiFi, Nexus 9 Cellular, Nexus 7 (2014), Nexus 10 and the Nexus 4.
The inclusion of such and old device like the Nexus 4 further emphasizes Google's impetus toward software update for its Nexus devices.
In case you are using any of the above mentioned Nexus devices as your primary phone, then it would be a wise decision to not flash the update manually onto the device. With every beta build there are a no of bugs, and that's no exception with Marshmallow factory image.
Google's initiative to push the Marshmallow update has also forced likes of Motorola, HTC and Samsung to work on the update for its range of smartphones. Apparently it's seems that the Motorola will push updates for its range of devices first.