Logged in at work (IE) to see how it works. The guide is pretty badly done, but I'm sure that will improve. The search feature on the guide didn't seem to work. The controls are hard to figure out. I only really saw one play button when I clicked on a show and it would ask "Are you sure you want to watch and record this show?" I saw no way to just watch a show.
All that said, the video quality was pretty good. Not full HD, but still pretty good. I didn't want to blast audio while at work though, so can't comment on the audio. I thought the quality was pretty close to what I have seen on WatchESPN while at work, and WatchESPN looks near HD quality when I'm at home. Unfortunately I am traveling for the next 4 days, so I won't be able to check it out on my HTPC quite yet, but I'm going overseas, so it will be interesting to see if it works when I am in Europe.
The whole concept sounds great, but outside of at least the recording, I have to wonder where it will go. My provider already has an app you can use on tablets and anything with an integrated display like an All-in-One or Laptop. I've used it and the quality is pretty much as good as what I get on my HTPC via InfiniTV. I like this nimbleTV idea because it is not restricted to those devices. If nothing else, maybe this will spurn Optimum to allow their App to run on normal PC's.