Will the new php 7 version be backwards compatible or will we face compatibility issues? Will it greatly affect the way we code for WordPress? My host offers php 7, should I use it for a WordPress site now?
WordPress has been preparing for PHP 7 for a while and, according with this announcement, WordPress should support PHP 7 since November 12th. According with the same announcement WordPress will still supoort PHP 5.2.4 as minimun requeriment, although it is recommended at least PHP 5.6.
The downside: there are propabably so many plugins and themes that are not compatible with PHP 7 that using PHP 7 or not right now can not be a general recommendation. If you use third party plugins you will have to test your sites one by one and ask to the support team of those plugins if they plan to support PHP 7.