Installing or flashing a new custom ROM is nothing new in the Android world. However, dual booting custom ROMs is still in nascent stages and available for very limited devices. Joining this list today is the Nexus 4, thanks to Multi ROM from oblikas.
Thanks to Multi ROM, Nexus 4 users can easily dual boot between multiple ROMs without the hassle of installing them every time. The MultiROM boot manager will appear every time you power on your device, and allow you to select the ROM you want to boot into.
Perhaps the main advantage of Multi ROM is to allow users to boot into two different kind of ROMs, like an Android based ROM and a secondary Ubuntu Touch based ROM. A point to note here is that the data partition is not shared between different ROMs, unlike MoDaCo.SWITCH for the HTC One. Another issue with the Multi-boot is that you cannot use it to multi-boot ROMs with different Android versions.
If the couple of issues mentioned above are not a deterrent for you, and if you are interested in multi-booting different ROMs on your Nexus 4, head over to this XDA thread for the full instructions and download link.