Technically, today was the "official" release date for these figures but stores have had them out for about a week.
I would highly reccomend picking at least one up if you're a Halo fan. I bought the GameStop Exclusive Steel CQB Spartan and the figures are top-notch. Great articulation (almost too much), unique paintjobs ("battle damage" and paint details on undersuit), Interchangeable armor, these guys have it all. If they were only an inch and a half shorter, they would be in scale with Star Wars and would blow Hasbro's work out of the water...