I had the 30-day trial from Nextflix and was doing it through my wii. The download typically took about 5-10 seconds. However, at times the movie would stop while viewing and re-calibrate. This was not often but it did happen. A couple times it never cam back on at all. I cancelled the sub because the movies avavilable instantly are not "new" movies. The plan which does not include DVD and instant streaming is cheaper but they have it so no really good new or semi-old movies are available without doing the more expensive DVD-instant plan which is more expensive. I will just keep stopping by Red Box on my way home for a buck!!
Pretty much what Wolfcub said as far as the DSL end of it. We continued our subscription, this combined with Hulu and antenna content my wife gets more quality (yeah that's debatable) content for less than $20 a month compared to over $150 a month with Direct. Only regret, no True Blood.
We've used Netflix through the Wii for six months or more. We rarely have any issues and LOVE it!! Prior to having the ability to watch through the Wii, we watched Netflix movies on the computer. The quality and flow seemed to depend on which computer we were using.
If you have a fast internet connection, you will have zero problems and there are fairly new movies and they add movies all the time.
We also cancelled our dish and just use Netflix and Hulu. On the $9.99 plan, we get unlimited streaming plus 1 DVD at a time. It's been a few months and we're still happy. Saves us about $60 a month plus whatever we were spending at the Redbox.