The mystery bags got a makeover - same concept, just new items.
In addition to some new items, players can now get 100 Free XP from mystery bags.
Here is what I have found so far:
100 Experience Points
Many different kinds of boosts
+5 Free Skill Points
+1 Reward Point
Chop Shop Items
Uilleann Pipes (St. Patrick's Day Collection Item)
Luck of the Irish
..and I'm sure there are a lot more items (feel free to post what you find in the comments).
The unfortunate thing that is a lot of these items are either 1) free gifts 2) easily gotten (chop shop items, boosts, etc).
There are still a few useful items (+100 XP, +5 skill points, +1 reward point), however, it seems that once again the "good" rewards are limited. Nearly everyone's first mystery bag seems to yield 100 XP, and the +skill points and +reward points are fairly rare. However, they're certainly better than nothing! The +5 skill point reward can go very far along with the extra stamina and energy each day from the chop shop!