We're impressed by teams that get things done, and unimpressed by teams haven't even started to build something. I've often found myself thinking, "If you think this is so great an idea, why haven't you spent some weekends building a version 0 prototype?"
Seriously, whether you're raising pre-seed from YC, seed from angels, or Series A from VC's, you've got to get moving.
This is not college admissions -- nobody is here to pat you on the head. If you want to get ahead, you've got to build, build, build. A great idea on its own is worthless without a team that can make it real.