Russia has banned the delivery of advanced S-300 missiles to Iran along with a host of other weapons. This has pleased the United States and it's allies. Russia has also banned the any visits to Russia by high ranking Iranian officials associated with their nuclear program
Al Jezeera reports, http://english.aljazeera.net/news/middleeast/2010/09/2010922164756103694.html, the U.S., Israel, and their allies are very pleased with this decision following U.N. sanctions, but they are still concerned with the sale of cruise missiles to Syria.
Although this decision by Russia is not likely to sway Iran away from it's nuclear ambitions, it is at least a sign that their former partners are growing cold over Iran's ongoing arrogance.
Whether this works to change their minds or not added pressure can only reinforce the worlds concern over Tehran's intentions.