It just takes too long to get to the mana levels you want for it but as soon as you start to couple it with Mana Vault, Grim Monolith and other such cards then it is just stupidly potent
If not, thats your step 1
If one player is just sitting behind an Island Sanctuary not doing anything, the other has all the time in the world to look for fliers, islandwalkers, enchantment removal, direct damage, whatever
Unnatural Growth and Zopandrel, Hunger Dominus both double your creatures' power and toughness at the start of each combat, while Defiler of Vigor, Quilled Greatwurm, and Railway Brawler all put +1/+1 counters on your creatures
Are there still boxes of Summer Magic floating around
You also have a range of video-game-themed cards like Level Up, which gives you double +1/+1 counters after attacking, and High Score, which lets you draw cards for having the strongest creature on the board