So for wild unfounded speculation's sake, how do we think these new mechanics will play in practice? My thoughts:
* +Buy will become less important, or at least face competition, since now you can cheerfully use your leftover cash on other things without the effort of picking up a Woodcutter or whatever. $2 cards may also face competition, although I bet we see an "overpay to gain another card" card which functions along the lines of "when you buy this +1 Buy"
* Cards that often lead to overpaying get stronger. I'm looking at Spoils, maybe Death Cart (although that's quite severe overpayment), Platinum (likewise) and probably some others.
* Planning is in, improvising is out of style (relatively speaking of course). You don't have to worry quite so much about shuffle luck since overpaying for the card you wanted won't hurt so much, and coin tokens obviously afford a measure of control over your cashflow, especially if they're available early.