I bought the Kärcher DS 5500 water filter HEPA vacuum a couple of months ago, and I absolutely love it.

http://www.best-vacuum.com/karcher-water-vac-5500.html

Never have my carpets looked this clean and it sucks up everything - from cat hair to cat litter in the bathroom, and everything in between.

I just pour out the dirty water when done, and solid things like hair and litter clut (SP?) together at one end behind "a wall" in the container, and are easy to throw out as well.