Dice K's got great stuff, but he's noticabley different from the wind-up to the stretch. Also, as is the case with most Japanese imports, he throws up the zone, which is not a good thing here in the states. He should be fine cuz of his stuff, but his mechanics are inconsistent. Watch the arch on his back, and notice how he has problems with accuracy when cuz he's bent back, as opposed to forward. It might take him a season like Beckett, I agree. Still though, great talent, just a little inconsistent with his mechanics and quality.
As for Okajima, his delivery is what's making him successful right now. It's very awkward, and nobody's ever seen it before. Personally, I can't see someone being dominant with an 86 mph fastball He could do real well against lefties down the road (his nice hook), but I think righties will eventually eat him up as the season moves on, and they get a couple of looks at him.