Yanmega Prime does 10 more damage than most other cheap attacks in the format (granted you don't need 1 energy, which isn't hard to get out anyway), with the requirement of playing a supporter every turn to do the damage.
Celebi Prime isn't very good because of the active requirement, the attack is okay, but most things can warp you out, or don't have to attack your active.
Psyduck: It just kills me to know it won't be called "Stupid Head" in english, just like I was pumped because Machamp's attack was called "drop" but was translated to "take out". I am interested to see what the english attack name is, though
Electrode Prime is one of the cards I like, since you can actually get behind with it to use Twins/Black Belt, I'm sure there will be a few decks that use him. (though I doubt tier 1, especially since if you use his power with gengar prime active, it's 2 free lost zones)
Machamp Prime is slow and, at best, will be featured as tech in Machamp SF (or the new one) decks.
Grumpig, yay psychic lock! And on spoink's evo, too! If there's ever a psychic version of Cherubi to increase the damage output it might see play, but 20 is way too low of damage.
Bronzong for legend decks is eh at best, I could see Bronzong/Electrode/Legends, but it's still a stage 1 to setup vs. using sableye which can get 2 pieces in 2 turns. Both versions are susceptible to judge anyway. Legends will definately find their way into the format, especially KGL and DRL.
Porygon2 in gengar prime seems redundant now that Twins is printed, Gengar Prime will almost always be behind, and Twins just offered 4 more slots to find its win condition.
Porygon Z looks worse than the promo one, who can possibly T1 fetch its level X for draw power and attack harder for less with some TMs, it might be a good tech in decks that really abuse trainers, but it is slower than the reliable Junk Arm.
Ditto I find interesting, seems like a neat tech, though it seems like next season benches won't be vital, and people will discard an uxie and shrug it off.
Kyogre/Groudon legend has potential, and a neat attack that mills and does spread.
Ray/Deoxys legend is probably the best so far, the discard hurts it, but if you can get it off 3 times successfully you win (WAIT BUT DPL PUTS DOWN MORE PRIZES! Shouldn't matter much, you set down 2 prizes, I OHKO you for 3)
Dialga/Palkia legend is probably the worst of the set, but is decent.
Twins is good, especially in gengar, who doesn't take prizes, but is really overhyped right now for any other deck.
Black Belt I see as a good card that is playable in decks that have prize wars and struggle to OHKO stuff (aka needs crobat drops, spray splashes, etc), but it's such a dead card early on without claydol to throw it back in.
Junk Arm will be good in Luxchomp and other decks that can amass a good hand size and have really broken trainers.
Rescue Energy is really nice for Gyarados, anything else it's meh to me.
Alph Lithograph is probably the first half useful one, seeing that eventually Azelf will be gone, and TPCi might view lithograph as a good enough replacement and not make a new similar card.
I'm quite surprised there was no card with a power draw such as Claydol or Pidgeot, I think Uxie will be fine, but knowing the previous set cycles, usually a card always replaces another such drawpower card. Magnezone Prime is okay in my opinion, but highly inferior to Uxie until lategame, when the match is probably decided. (It'll have its place in a few decks)
I also really feel that they should have printed a Gengar counter, like a basic pokemon that whenever it's returned to your hand you can discard it (to prevent the Hunter combo) or even a card that recovers stuff from the lost zone (though that would face abuse in the form of Palkia GX and coming into play powers). Gengar will probably dominate next format, and twins/black belt do nothing against it except Twins helping Gengar. Meh, hopefully a counter will arise in Black/white sets before nationals/worlds.