OSX Mavericks horizontal scrolling doesn't work well in Finder?
No. Horizontal scrolling is butter smooth in Finder for several of my machines. I've tried several different resolution settings on the Retina MBP as well as tried mouse and trackpad scrolling on older machines with less CPU / GPU power than the 13 inch MacBook Pro.

None lag in any manner scrolling horizontally as opposed to vertically in my experience. Due to the voting on this question, perhaps there are some issues for certain configurations or something else that I'm doing differently than you, but even for all different views (icon, list, hierarchical, etc...) and finder windows with a thousand files in the folder, I'm not able to see slowness when scrolling horizontally.