I use it, and would recommend it. My camera is not great in low light situations so was looking for some software to help. I read about it in several photography magazines and it was highly rated for it's capabilities for a lowish price. It's not essential, but a nice thing to have:)
I use noise ninja and recommend it too. It uses noise profiles for each different camera that they supply or you can create your own profile. So far I've only used it for my digital images and haven't gotten around to doing a profile for my film scanner. Also Noise Ninja is built into Bibble Labs raw software. I haven't heard of Neat Image so I don't know which is bettter.
Downloaded and installed the latest Noise Ninja and it worked much better than Photoshop's Reduce Noise or Neat Image. lots of variables to play with and camera profiles to match your cam. excellent product.