I've been running PS/CS5, along with AI and Id, on Mavericks for several months. It's stable and runs about the same speed under Mavericks as it did under Snow Leopard on the same MacPro (late 2009, dual-quad core, 16gb RAM).
The only issue I've seen has been with cursors. The tool cursors don't accurately show the actual size (Brush, Paint, ...) and occasionally the cursor will vanish briefly when the machine gets a tad busy in the background (Panning across a 2gb PSB file with 10-20 partially masked adjustment layers to render at %50).