What is the recommended version of python to use with openerp/odoo? Is it 2.7 or 3 All these days I was using 2.7 if I choose ver 3 will it cause any problems?
I won't work yet with python 3. The best python version to have is the highest 2.7.* (at least 2.7.3).
You can see the major dependencies and python version in the installing tutorial:
On my operating system, python 3 is the default so to start an instance without using a bundle (in my case I clone the github repository), I use this command:
python2 ~/path-to-my-odoo-git/odoo.py -d odoo-test
As for when odoo will work with python 3, there is a number of needed python package dependencies not already ported to python 3. Even if they were already all ported, Odoo itself would take some efforts (without talking about all the ecosystem of custom addons which would get unusable untill ported).
So I guess it will not be available before 1 year and most probably not available before 2 or 3 years.