Yes, it's severe, it's like one player starting the game with a Laboratory in their starting deck. It's not like other trashers (except Cathedral) because with other trashers you have to draw and play the card to trash it, you don't actually get to trash something on turn 2. It doesn't matter whether you buy Chapel on turn 1 or turn 2.
Please tell me, I want to learn from you, more advanced players:
With my project at $4, if player A buys it on turn 1 and player B on turn 2, in first shuffle decks will be:
Player A – 7 Coppers, 2 Estates and a $3 cost card
Player B – 7 Coppers, 3 Estates and a $3 cost card
Of course player A has more chances to draw a hand without an Estate, but in this case he would have to exile a copper, decreasing his buy power this turn, or get an Estate back. Even with this factor, is player A advantage so enormous?