If I had to bet, I would place a large sum of money on this card not being good enough for competitive Vintage.
If you are casting this card on turn one, say off a mox, then you would need a threat, a land, and a piece of disruption to ensure your threat resolves. If you are not casting this on turn one, then I fail to see how this poses any relevant threat. For 1G, there are much better cards that you want to resolve in Vintage. Hell, I would want to resolve Sylvan Library more than this thing.
I think people are putting too much importance on this card. It is NOT a win condition. It is a utility creature and can fuel a multi-colored aggro deck with a chance to *maybe* combo out.
Good point about casting on turn 1. If you cannot, I would be happy to have Duress/Thoughtsieze turn one OR have FoW backup and cast him turn 2. The deck should be G/B or G/U or all 3(or more) colors. If you have Dark Confidant drawing you cards this snake is going to let you cast some serious spells. Imagine if you add in Vexing Shusher(GG) and with the extra mana make all your spells uncounterable. Great with/against CotV btw. Broken? No. Consistency should be more of a priority.
For 1G I would rather resolve Oath than Library, and thats not going to change anytime soon. Turn 3+ I would rather resolve Regrowth. A deck that NEEDS to resolve this guy is going to fail. A deck that UTILIZES this guys mana smoothing and potential acceleration has a chance to succeed. Aggro seems like the best shell to me, you can now play with some hard hitting 3-4 cc fatties that dont die to pyroclasm and increase your clock. Seems fair to me.
I still stand by my statement that this card is good, but not great. For TWO whole mana I think he can find room in a Vintage deck...
