Yep, I originally went out in search of Lack shelves to make Stairway to Cat Heaven, but I'm actually really pleased with how these turned out. Way more design-y. After I made it, I actually found another site that had used BJARNUM shelves for cats, but they didn't top them with nonslip rugs, so I'd be afraid of, as I said, sliding kitty death.
Edit: Here's another site that inspired me,
http://katwallks.com/ They sell their version for between $30 and $50 a shelf, and they don't look nearly as nice (IMHO)...not something I'd want in my living room.