I feel like this format is quite a change from the slower, grindier formats we've typically had for the last couple of years. Board stalls do happen, but more frequently games come down to one player curving out and beating down, while the other player tries to stabilize. Also, there are few creatures that block well in the early game, and a lot of removal and combat tricks that punish double blocking.

As a result, I think you have to be particularly careful about blocking if you aren't the beatdown in a given game. Often it's better to take the first few hits and build out a solid defence for the mid-game than to offer trades early and get blown out. If you're beating down and get to trade 1-2 mana combat tricks for decimating their board, you almost always win.

Neal Oliver had a good article on CFB last week that crystalized this for me. (http://www.channelfireball.com/articles/racing-in-kaladesh/) I've noticed some of the better limited streamers taking these sort of lines in Kaladesh draft.