how much more impact the "hard" portion of your project can have if intermixed with a touch of suspence, and maybe a few seconds of silence.
This is actually my trouble with Slipknot - a lot of what I've heard from them is a lot of 'hard' stuff that could be so much more interesting if they spent more time dealing out texture and variety in-between. Though I can't say I have heard very much.
If you're aiming for a project, I think there's two options (or a combination) when it comes to making it interesting: either you make it very thematically and visually cohesive, or you look for maximum variety (or both). The latter approach seems to dominate all good recent projects. The former approach hasn't been explored very extensively yet, there's only bits and pieces of it (that's why I really hope Pen-Pen can get the LTE project off the ground, it shows a lot of promise in that regard).
So if you're going to make a Slipknot project, don't go for something that will end up looking like a lot of random explosions and blood to an hour of banging and yelling. You probably won't be able to make it a 'unified concept' kind of project, but you can get it done well with variety. Look into all possible tracks carefully, and try to arrange them in as much variation as you can.
Anyways, good luck. Though myself, I'm not interested in participating unless someone shows me a track that has as much variety and musical texture as I've been saying Slipknot can realistically do, but seems not to want to...
Still, eh, if there's been a Korn project, Slipknot deserves a shot too...