Why wouldn't miners reject interactions with miners who set the block size too high, for instance?
Yes, I believe they would. So far, most miners and pools are VERY conservative; I think the idea that they will create huge blocks that have a significant risk of being rejected, just so they MIGHT get an advantage over marginal miners that can't process them fast enough, is loony.
But I might be wrong.
So I'd like to wait a little while, think deeply some more, and see how miners and merchants and users react with the system we've got as transaction volume increases.