I don't remember the exact details as I opened my 1st pack at a pre-release, but my first pack had a Charizard and a Steven's Advice. However I didn't pull an ex until after the pre-release was over... (I pulled a Claydol EX)
Well, I got...
2 Sharpedoes
Prerelease Cacturne
2 Omaster
Kabutops
Slaking (traded for Kabutops δ and Mightyena PK)
Lanturn
Medicham
Gardy
Cradily
2 Magnetons
3 Battle Frontiers (Traded one to LV 'cause it was holo, should've asked for a strange cave)
Zangoose
Made many alterations to my decks. Especially the Fossil one. And yet again.... NO EX's.
I still haven't bought any yet, but I'm hopefully gonna get the dusclops deck and 1 booster today. The theme decks are never amazing, so I edit them alot until something like a 4-2-1 line becomes a 2-1-2 line. It really annoys me that they always have the 4-2 lines. I use to just take all the good cards and lines out and buy boosters until i have a stavle deck, but i ended up with loads of other useless pokemon that i took out which no-one will trade for. Hopefully I will get my 5th ex in Power Keepers.
I can't remeber the first pack I opened in the prerelease, but I did get the following at the prerelease; Metagross Ex, Delcatty, Raichu, Magneton, Lanturn.
I got Carvanha, Baltoy, Poochyena, Skitty, Seedot, Firestarter Blaziken, Lightning Energy, Sealeo, and Glacia's Stadium. For some reason none of the cards are rev holo...