I use the tv show downloads 8-10 times a week depending on how busy a week it is. Stuff like Walking Dead, etc... are 1080p/24 files and the PQ is outstanding. It looks better than anything I can do streaming, and especially the HDTV version on Directv. I love it.
I have never seen any Amazon streaming look that good, but I only have a 6mbps connection. I like the downloads because I buy the series pass for a show to get the discount, and it auto downloads to the tivo the next morning when Amazon puts it up. This way its in my playlist in order with the other shows I recorded off antenna. Very convenient.