Bummer that it's only on Windows. It's a casual game, while I spent plenty of time on my Macbook on rather more dedicated games. DirectX 11 is probably in the requirements simply because no one bothered to check with previous versions (however Wine on Mac doesn't properly support DX ≥10, and VMs have trouble too, plus Steam doesn't work under Wine on Mac).
Still missing the best of the Katamaris, though — the second PS2 game — We Love Katamari. Best level designs and stunningly good co-op play. They are leaving money on the table by not porting it.