So...here's the question... if Powell was right - where's the uranium that these tubes were going to enrich?
There's uranium [link|http://www.iaea.org/worldatom/Press/Focus/IaeaIraq/unscreport_290103.html|in Iraq].
Iraq had successfully concentrated uranium from its own ore and produced industrial quantities of feed material (UCl4) for electromagnetic isotopic separation (EMIS). There were no indications that the production of feed material for centrifuge enrichment (UF6) went beyond laboratory level.
As we know, absence of evidence isn't the same as evidence of absence. We can argue about whether there's reason to agree with IAEA's conclusions about Iraq's nuclear weapons program, or whether to agree with the US and UK statements about it. We can argue about whether the aluminum tubes in question were useful in a centrifuge program. But it's clear that Iraq had the knowledge and the means to produce weapons-grade uranium.
For me, it comes down to Iraq's behavior. Iraq gave little reason for others to believe its statements that it had ended its prohibited weapons and missiles programs. It was still importing prohibited materials (as the aluminum tubes were even if they were only for rockets) in contravention of the UN sanctions. It never, as the UN demanded, fully accounted for the materials it claimed to have destroyed. It was still playing games with the inspection process - not giving a full accounting, threatening scientists with death if they were interviewed, etc.
My $0.02.
Cheers,
Scott.