Summary: At this point, as most of you already know that the Set.2 cards are out in Japan for couple days (they released two days prior to official release). Several people who have purchased boxes in Japan started to report the difference in the chance of winning URs in the Set.2 box.
First of all, you need to know that a booster box in Japan contains 12 booster packs i.e. 3 Japanese booster box equals to 1 booster box in the U.S..
In the past with Set.1, pretty much most Japanese booster boxes had on average 1-2 UR(s), which was consistent with 1:60 (=1 UR in every 7.5 booster packs). As far as what I have heard in the past, with Set.1 box there were people who got lucky and pulled 2 URs from one box, but to compensate this there were people occasionally with 0 UR. But again majority had pulled 1 UR per box. The important thing here is that I have never heard anyone pulled more than 2 URs from a single booster box in Japan with Set.1.
Now this has changed with Set.2. There has been numerous reports that some received 3 or 4 URs in a box. Quite few had 0 UR in a box. More interestingly, there is a person who pulled 2 phantoms, 1 ultrarare from a box with several extra rares and many uncommons without any common. Whether this last box was due to mis-packaging or intentionally created by Sony is still unknown.
Some people claims now the UR is 1:70 rather than 1:60 with Set.2.
Whether this is true or not is still uncertain since the booster pack package picture was not uploaded with the above statement. But to me more important issue here is the random mix of Set.2 booster box content in comparison to the Set.1. If this applies to U.S. and/or UK version of booster box, we will no longer be guranteed for minimum 4 URs (average 5 UR) per booster box. Sure still it will average out in theory, but would you want to spend $100+ and get 0 UR? I’d rather be guranteed with 4 or 5 URs for my $100.