Same flaws as the card game What flaws there are with Arena are, fittingly, the same flaws you can identify with Magic: The Gathering
As for the best of the new creatures, O'aka, Traveling Merchant turns your excess counters into carddraw, and Maester Seymour grows creatures of your choice as you grow him
If, for some reason, you're looking at a Pokmon card to buy, but you can't physically hold and inspect the card for yourself (for example, if there's a global pandemic, the shops are shut, and you can't go within two metres of another person), always ask the seller to take an original, high quality photo of both sides of the card for you
The key variables are clarity and lighting a focused photo taken in natural light will print dramatically better than a dark, blurry crop from a group shot
As you play a card with an Adventure, you choose whether you are casting the permanent spell or the Adventure spell