Just as an update: I just today had my very first game where the Eidolon came back to bite me hard. Found myself at 4 life and if only I could cast two spells from my hand I had a good shot at winning, but with an Eidolon on the board, the second spell would have killed me dead. :P
Anyway, after some more competitive play, plus some testing, I've decided to adjust the deck a bit. Biggest change is dropping Trumpet Blast in favor of Hammerhand. When TB goes off big, it's crushing, but usually the deck is already winning at that point, so who cares? In other board states (developing, parity, losing) the trumpet blast is a disappointing draw. On the other hand, being able to bump Rabblemaster's toughness to 3 AND haste him when he comes down on turn 4 is HUGE.
The biggest threat to this deck is removal that wipes out all these 1 and 2 toughness creatures. This shows up when comparing games where the Hall of Triumph actually gets played (very rare since it's a one-of) and those where it does not. To that end, I'm moving the second Hall from side to main right away.
While doing all that, I've done some tweaking in the sideboard, too (adding Crater's Claws for reach when Green+whatever decks stabalize just out of kill range, for example). The deck is changed enough that I'm just going to put up a new deck instead of editing this one.
The new deck is at: