I read a very nice post here.* I see the idea of Israel’s obligation to the Torah serving as the primary function of the mission that they were chosen to perform, which is that of setting an example of holiness and obedience to the world. It is what they agreed to do (as if they had much of a choice at the time 
. While the obligation for observing various precepts and commandments rests upon them, the Torah continually discusses inclusion of outsiders rather than exclusion.
With regard to Gentiles or the Nations, I appreciate this idea of fulfilling a mitzvah (read the referenced post for context), in and of itself being a sign that the individual accepts the commandment and thereby accepts and acknowledges that Hashem truly is God. I think this goes a little way to cracking the identity crisis that many are struggling with.
The commandments are a light. When we are focused on them and Torah life, it is sanctifying. In my personal life recently, I have experienced less prayer and bible study due to an extremely busy Fall/Winter. It has affected me. I currently feel closer to worldliness than Godliness. The Sabbath has been a weekly reminder of what I long to strive for, holiness not just once a week but every day. Fulfilling commandments is not the objective, though it is a byproduct. Living a sanctified life, empowered by the observance of mitzvot, truly shines a bright light when so much of the world is continuing in varied levels of dim light or even darkness. It is thanks to God first, and also Israel that we are able to attach ourselves closer to Hashem through study and application of His word.
In summation, the more mitzvot we observe, the brighter our light is. Which is good for us, and good for others. It is all too easy to keep our light hidden in the world. Even if we are genuinely nice, servant-minded, humble people; what causes our light to stand out? In my view it is a proper understanding and application of the Torah that our forefathers in Christianity sadly cast aside for too long.
* http://christian4moses.wordpress.com/2010/12/24/rationale-for-observing-commandments-other-than-the-7/
