Algae,
I actually have two Roku units, one on my main tv and one on my smaller one. So you can see I am happy enough with Roku to buy a second one! Besides Netflix, they stream many other "channels" and services such as movie and tv programs through Amazon, photos on Flickr, music from Pandora, and many, many more. And they are adding new channels all the time.
This is a great alternative if you don't need a gaming console, and like others have mentioned, it is really simple to set up and very straightforward to use. And all of this is available with only a monthly subscription of 8.99 from Netflix. This is the same subscription rate on the Wii but through the Wii you don't have any of the extra services.
Just my 2 cents on the matter,
Jean