I haven't tried it myself but the general concensus is that most will not use it. There have been a few incidents I think where it was used but only when there were no natural nesting sites available in the immediate area.

Penny

I have one and it has been up 2 years now.
Ruby Throats won't use it.
Mine don't even check it out.

I have provided a link for information about the hummingbird house from Bird Watcher Digest. It does work according to Bird Watcher digest's article. You can see the house at the following web address.

http://backyardbirdwatcher.safeshopper.com/71/1315.htm?999

Here is a link that might be useful: Bird Watcher Digest