Will upgrading a Nexus 4 to Android 5.0 require a "reset" My Nexus 4 has been bugging me that a new Android is available, since a few weeks.
However, I read somewhere that upgrading would make me lose my data and have to re-install everything. Is that really the case ? (I find it strange that it would be so insistent, if it were true that this causes loss of data/setup).
There are two ways you can upgrade your device to a latest version of OS:


OTA (Over The Air): This type of upgrade will automatically take care of all the steps required to update your system. The once which you are bugged with is OTA update. One needn't erase data while upgrading using an OTA.
Flashing your device: Usually Google releases device specific factory images on its developer website along with the OTAs. But for this, you will need to erase all the data on your phone and install the factory image.


In your case, you have received the OTA and it's ready to install, and hence shouldn't be worried of losing your data, neither you will be asked to re-install. However, it's always better to have your data, app data, etc. backed up for the worst case scenario.