I tried to use Plex once, many years ago, but they did not support HDHR Prime at that time. Tried again few years ago, but no free trial to test it out...no thanks. The Plex server my buddy has, ugly...hate the look of it. Seemed to work ok though.
Emby was great for me and I have been using it for several years now. I switched from WMC to Emby. It was easy enough to setup and maintain.
In the last year, they have very much unified their web UI and apps.
I my self have had detailed communications via their forums with the devs and helped test and resolve issues that did come up over the years. Their desktop software (Emby Theater) is my favorite as since it uses MPV as its back-end player, i can use a custom .conf file and tweak some things to enhance the video quality.
Emby is far more polished and modern looking UI than Plex or Channels. But those are software's whose primary goal and usage is as a home media server, with Live TV/DVR as secondary feature added in. Channels (and HDHR software) primary function and goal is Live TV/DVR.
I am happy with Channels DVR, but I do think it needs more work, more access to advanced settings and configurations for us advanced users, and UI refresh and polish (with a black theme).
Regardless, since I discovered Channels DVR few months ago, with its TVE ability, it very quickly became a reality to allow me to drop Comcast CATV that I have had for 35yrs, sell my Prime tuners and switch to streaming and OTA for TV via my Nvidia Shield.
(The money saved per months, after about 6 months, I calculated, will pay for the equipment I had to buy to make the change over (2 Shields, HDHR Q, Antenna, cables, etc) )
While, yes, Channels at $80 a year I think is high compared to others, I do believe it is well worth it. I can only hope that the cost does not increase though, not with out some big major reason/incentive/improvement that requires it.
As far as lifetime price not being sustainable, well, both Plex and Emby are ticking along for many years with no issues. But each company is different....with overhead, commitments etc. I can understand if Channels can't do a Lifetime plan for those reasons of sustainability...only they know their accounting.