It's nice that you try to keep up with important topics, but you've made a number of mistakes here.
1) You're talking like the topic just came out of the blue, while in fact it's been digested for many months if not years in the Pol-US relations.
2) Russia loves to flex its mussles and threaten countries that not long ago were their lieges. But that talk of preventive strikes is nothing but working the public opinion (especially the Russian one before their elections) and such sentences are usually uttered by some hawkish Russian generals. In actuality, the Russians have put their tone down recently. I especially encourage you to read about the latest meet-up of Russian and Polish foreign ministers - Lavrov and Sikorski.
http://www.warsawvoice.pl/view/171053) I believe the report that you're referring to was the US's own NIE, and not IAEA's.
4) The main purpose of the Polish interceptors is to protect Europe (and US only in some scenarios.) The location in Poland is justified by the most probable paths of missiles fired from Middle East (esp. Iran), and Poland's location more-or-less in mid-Europe. And the reasons for protecting Europe are two-fold:
a) because US has the obligation to protect other NATO members (and vice versa) - and the MD protects quite a few countries from long-range missile threat, and

so that US's enemies won't blackmail States that if they can't hit US, then they'll hit their European friends.
5) The interceptors are not armed with warheads, so they make very poor offensive weapons. They use their kinetic energy to destroy enemy missiles with a high-speed collision.
6) There's no possibility that those 10 interceptors could prevent the Russians from launching a nuclear attack, as they have hundreds ,if not thousands, of missiles.
[Although there's one logical argument that many miss: if US and Russia were to wage war, then if US hit Russia with an intention to destroy their nuclear arsenal, there's a high probability that a couple of missiles would survive and be launched against US or Europe - then 10 interceptors could make a world (or millions of human beings) of difference.]
7) When graemesmith suggests that Russia has the right to be nervous about missiles being installed near their borders, then I would suggest two things:
a) Poland is a sovereign country (unlike before 1989). It has the right to invite US missiles, or Russian, or Chinese or Iranian or whatever it likes for that matter.

If Russia can moan about missiles installed close to them, then Poland has the same right and hereby as a Polish citizen I demand that all Russian missiles are moved out of 1000 mile range from Warsaw.
8) Iran might have withheld their nuclear program, but they keep developing long-range missiles and they're not secretive about it. Why do you need a long range ballistic missile if not to deliver a high-profile load (eg. nuclear)? Would you shoot 3000 miles away with a 500lbs worth of TNT? To do what? Hope for destructing a building? These weapons aren't that precise, these are not cruise missiles. That means - Iran is not nuclear now, but they're keeping their options open and some think we should prepare for the worse.
9) And I wouldn't agree that it's a missile crisis. Russians can shout as they will, but neither can they do terribly much, nor does anyone pay that much attention. Yes, US Govt figures meet with Russians every now and then to show good will, but keep in mind that Russia is not half as powerful as it was.
And things are actually sorting out recently. Sikorski and Rice have now agreed on principles, PM Tusk will visit US soon and bring the deal even closer. And Russians will eventually say "we're not happy with what happened, but so be it."
If you wish to discuss this topic further, mail me at axure (at) wp.pl 'cuz I don't think I'm gonna visit this site very often, I just got here by accident (a Google search, to be precise.)