I can't wait to see the LEGEND cards to see if they have attacks worthy of their struggle. With rumors of Legend Box coming, I think Rayquaza/Deoxys could have some real play (Without having to deal with dual type themed decks)
Especially if they don't have terrible weaknesses. Groudon/Kyogre will have either Water/Electric, or most likely Grass/Electric.
Rayquaza/Deoxys would probably have Colorless/Dark weakness, which is playable. Probably means their attacks won't be spectacular. Resistance to Fighting...
As for the Primes, I like them all, but I can't say any of them are game changing. I got chided (unfairly...
) about how Houndoom's power isn't that great, but there aren't that many cards out there nowadays you can focus a competitive deck around. Gyarados, Chomp, Ape, Blaze, Luff, Phan, Flygon and Luxray are the only things around. Houndoom I think is just a neat little stage 1 that could get an extra prize from the bench.
Slowking I'm not too wild about, yes it could be combo'd with underground, etc. But if your opponent controls the card, it may as well be Noctowl that has a little more buff, and a Vanilla (underpowered) attack.
Raichu may be playable, especially since level X is still around. Powerful, but you need Fisherman or something to keep it going, not to mention you gotta watch out for Donphan decks.
Scizor reminds me of the old school Water Gun pokemon, where they do a set amount plus 20 for each additional energy...I don't think his PokeBody is game changing, besides DCE. Not to mention special conditions and damage counters can work around that. Donphan, Gyarados, and Jumpluff can break through this thing.
Espeon is interesting, but takes a bit of prep for it's power to be truly utilized. I'd like to see a quartet of eeveelutions on the field.
Umbreon has a built in SSU, and an attack that can do (in the absence of special dark and ebelt) 90 damage for 3 energy. However, you need 3 Eeveelutions on the bench for that to work, and I just don't see that consistancy.
It's strange, all 6 primes are stage 1, and you gotta be goooood to be competitive at that level.