Not necessarily the tools, I still can't afford most of them, but the metric system. I bought a Domino DF700 XL a year ago and I simply cannot wrap my head around SAE measurements when dealing with Domino tenons and getting the right depth, thickness and spacing correct. I picked up a cheap Starrett metric tape measure and all of a sudden my accuracy on everything is improving. It's so much easier to do the math, no matter how your project is laid out. 1/2 mm is easy to read on a tape and that gives me nearly 1/64" accuracy. I feel like I should be doing everything in metric, at least for cabinetry and furniture. Even for non-Domino stuff I find myself reaching for the metric tape more often than not. Any of you American woodworkers switched over to metric in your woodworking shops?