The Galaxy S3 is definitely Samsung's biggest launch so far, with 9 million pre-orders even before they launched it in any country. But there seem to be at least several issues that are delaying the Galaxy S3 launch in US and some other countries. The first and possibly the biggest problem is the pebble-blue version of the Galaxy S3, which seems to have been flawed right out of the gate, and Samsung already had discard half a million of them from production.
What's worse is that it will also cost Samsung a whooping 2 million units from being shipped in Q2. Those shipments may or may not be recovered in Q3. By then people might be looking towards other smartphones, so Samsung might recover only a portion of those 2 million lost sales. Lucky for Samsung, most people think that the white version is the "best" one, so with this they've avoided the problem becoming much larger for them.
I've never really liked the pebble-blue color myself. It looks too much like black, and the "metal-feel" (even though it's just plastic), makes it look cheesy. From the earlier rumors about Galaxy S3's colors, I was hoping for some real blue color, which I think would've turned a lot of eyes. But Samsung decided to go with a "safer" color unfortunately, just like its overall design.
Another issue that has caused Samsung delays at carriers in US is the little availability for the Snapdragon S4 processor that comes integrated with LTE, and it seems this has already pushed the launch of the Galaxy S3 in US by almost 3 weeks. Hopefully there won't be anymore issues, and Samsung gets everything together. There are a lot of people who are still waiting for the Galaxy S3 to arrive, in any color.