we don't advise anyone to use nightly builds in the production environment as sometimes major bugs can be pushed to nightly build, but in some cases upgrade to nightly build is required to fix some issue so basically if your project isn't mission critical and you are flexible / agile enough you can use nightly builds.
Another question, is it ok / safer to use nightly build for production / on live website ? since nightly builds are also like beta version so just want to make sure ?
We have announced V5.0 release date although we had to push 4.7 release date a bit further because we included some 5.0 features in 4.7 like responsive design. Upgrading to 5.0 will be a matter of doing some changes in your custom calls to the repository, bll layer and some utilities as 5.0 uses DI. So other than that I don't see any major obstacles in upgrade process.
When next version will be available i.e. monox 5.0, what difference it will make in upgrading process ? if I am using 4.7 (official release) OR nightly build ? Usually upgrade only support previous version so I just wanna make sure how it works in monox project ?