This is definately good for Iran. With their indigeneous missile capability and with the S-300 in their hands they will have a more solid and viable defense every passing day. Surrounding Israel with enough missile fire power will bring them to their knees. Iran and its arab allies may not be fully there yet but their capacity is in fact growing rather than declining. Israel missed the opportunity to make peace in the early 90s when it was in a far more better strategic situation.
First refugees travelling on Hungarian bus arrive at Austrian border (Reuters)
from the article: Iran official: We have obtained the S-300 missile system