Hi Muhammad
Here is the guide about NX-OS version numbering:
http://www.cisco.com/web/about/security/intelligence/ios-ref.html#11
1 or 2 are minor releases. Usually they contains fixes and minor changes.
Here is the link for release-notes page:
http://www.cisco.com/en/US/products/ps9670/prod_release_notes_list.html
You can compare release 1 and 2 in any train to check whether they fits your requirements.
For the latest released nx-os version release-notes wil be available shortly.
HTH,
Alex