We got our Netflix WatchNow disk for Wii today in the mail.
Surprisingly enough, it was in the form of an actual disk. I suspect that Netflix would have preferred to make the app available for downloading as WiiWare. But my guess is that Nintendo would have insisted on charging too much for the privilege. So a disk it is. And sure enough, you pop the disk in and select it from the "Disk channel" and fire it up.
The first time it phoned home and presumably noticed that it wasn't activated, so, like all Netflix devices, it put up an activation code and directed you to type that code into the Netflix website. It then immediately displayed the Instant queue, just like on the Roku.
The first surprise was that, though it wasn't obvious, it is possible to see other lists besides the instant queue. In fact, there are multiple lists, some genre based, others of various suggested titles... It was a nice surprise.
The navigation is fairly natural too. All in all, the whole solution is very Roku-like (as opposed to how TiVo works).