I own the figure and love it. I second everything TimothyR has said about it. It's a joy in all aspects.
That said, had I known that a Diecast Mk6 was in the works, I would've passed on the Mk45. Long story short, I was impatient and wanted to break into HT. I wanted IM and WM representation. So I opted to PO their newest versions (at the time), AoU WM and the Mk45. Knowing what I know now, I would so trade them in for the dc WM Mk1 and the dc Mk6 so fast it's not even funny.
That's just my perspective though. If it were up to me to leave one armor out (between the 45, 46, and 6) it would easily be the 45. Amazing figure, but the 46 and 6 were exponentially better than the 45 on-screen in terms of action sequences. Once you get beyond its uniqueness (in terms of appearance) it is such a disappointment. The Mk45 in Sokovia and the Mk7 in New York are such a stark contrast from each other in terms of final Avengers battle armors. IM2, Avengers 1, and CW really showed how to do Iron Man justice in a final battle.