I think we learned our lesson about the draft in Vietnam. Overall, you get inferior quality troops with low morale. These take higher losses. Higher losses lead to political defeat (sans a dictatorship and "total war"), stifling and/or ending your war effort.
As for the Iranians... people do realise this is the same army that only fought the Iraqis to a standstill, devolving into a war of attrition.. right? I'd give them about the same chances people gave the elite Medina Division... very strong... until the steel rain started.
I'm all for the Israeli's dropping a smart bomb on Iran's nutcase president before he turns into the next Kim Il-Jong... but if they do, and their's a coallition invasion, wow... gas is going to get *really* expensive. Everybody add Exxon, Shell, Occidental, & BP to their portfolios yet??