I think this Is a great application once they can get it to work properly. I'm not posting to "bash" Ultraflix but to tell you the facts as of this date. So here is my story.
I see all the news about Ultraflix and that Interstellar is available in 4K. $9.99, ok a little pricey but i'll try it. Mid-day I go to the SmartHub, create an account, look at the Interstellar trailer and everything works fine. Later that night about 9 pm EST, i'm all ready, can't wait, start the movie. The movie starts and about 2 or 3 minutes in, the movie freezes, then starts, then a couple of minutes later freezes, starts, etc, etc. So I pause the movie, go to the settings and notice that you can change the download speed settings. Mine was on Auto which is supposed to find the right speed for your connection. I change it to 12 MBS, still no good, then to 10, then to 8, then to 6. At 6 MBS it only froze every 15 minutes or so. OK so i'm able to get through the movie but with all the stopping and starting, it really ruins the experience. Also I noticed that when you get a lot of action, i.e. a lot of data needing to be transferred, the movie freezes and these are usually the best parts of the movie! Also the application tries to keep correcting by slowing down the data transfer speed to stop the freezing and in doing so you loose resolution AND they slow down the Audio stream as well meaning i'm starting with Dolby Digital then it changes to Dolby Surround. To add insult to injury, although I was getting Dolby Digital audio when things were working, there was no sound coming from my center channel. I tried everything! Even went to another streaming site to make sure it wasn't my equipment and played the trailer and the audio was fine. At the end of the day, it was a terrible experience.
I have FiOS with a 75/75 mbps hard wired link to my Samsung HU9000 and I have absolutely NO problems with Netflix, VUDU and other streaming services so i'm not sure if Ultraflix just doesn't have enough servers or high speed links to the internet.
I applaud Ultraflix for providing a 4K service and I love my Samsung HU9000 but they are going to have to evolve before I will ever rent another movie from them.
BTW, I had to watch Interstellar the next day in order to better understand the movie and there was a Samsung update with a new version of Ultraflix, I think it is 1.7, but no change in performance of the application. I got the same terrible experience until the app slowed down the speed to where I was probably watching 1080p or something in that range and it still froze!