Initial setup went fine, although I was unable to get MoCa working over my cable connection. Ethernet works fine and I happen to have Ethernet everywhere I have cable outlets in my home, although I would prefer MoCa to save network ports and avoid interruptions if my switch or router is acting up.
(UPDATE: Found out that MoCa wasn't enabled on the Premiere XL4, once I changed that it worked great on first try!)
I didn't have a problem getting everything working once activated and connecting both to update their account information.
-I have noticed that it hangs when trying to open the App for web videos hotlist and I have to power cycle to recover.
-I also notice that I am unable to play shows on other TiVo Premieres in my house. I have two Premieres and when I try to play from them it goes into a loop of folder after folder with alternating names.
-OnDemand isn't working, it shows up and I can browse, but choosing to watch anything fails with errors. My main unit is working fine with OnDemand, hoping that this is temporary. I may call Comcast and have them hit the cablecard with the authorization because I know before this was a problem.
(UPDATE: Found out that OnDemand won't work without assigning a tuner form the main TiVo. This is a very poor implementation, since the TiVo should be coded intelligently to notify the user that OnDemand is unavailable due to a tuner not being assigned. This won't be as much of an issue once dynamic tuner allocation is enabled, but until then I don't want to block a tuner for rare occurrences.)
-Lastly, it is unfortunate that it does not support playing videos using TiVo Desktop or others like pytivo. I am aware there is some streaming support, although it is not very good. I am hoping TiVo releases an app in the future to support DLNA or some other method of watching videos on the mini from a computer, since that is something I do often.
Otherwise, it works fine and is about the same performance of my Premiere, maybe slightly faster, but not as much as I was hoping. It is nice not worrying about a cable card and hard drive that can fail.
I really hope that they continue to improve the experience and allow more options as others have mentioned such as longer timeout than 90 minutes and future support of dynamic tuning from the Premiere line.