I would like to get back on topic because I hope to be cutting the cord in a few months and I'm going to need an OTA DVR solution. The contenders right now are the Amazon Recast or the new Nvidia Shield.
The Recast has a few peculiar limitations (HD-lite 1440x1080i, Fire TV clients only, no file transfers off the internal drive) and the reports of late have been not entirely shiny with respect to successfully recording all chosen events. The requirement that all viewers are using a Fire TV streamer probably isn't much of a hardship as they're relatively inexpensive.
The Shield TV Pro is a great streamer but perhaps not as great as a media server. You can outfit it with an external (or network) tuner and use the pre-loaded Plex Server (with a Plex Pass subscription) or the new (or coming soon) Shield DVR software from Tablo but media servers are really best when you can inexpensively upgrade them (i.e. cheap, high-capacity 3.5" internal drives). The Shield TV certainly has the horsepower to do any transcoding that needs to be done.
Once you get a "real" media server, you start finding all sorts of interesting uses for them (like hosting your entire digital music and video collections).
I use Plex (with a lifetime Plex Pass) installed on a retired computer (Athlon XP) using a canned Ubuntu Linux installation from Plex. No command line Linux required. I believe the Plex client software is now free of charge and there are clients available for all the popular streamers.
I believe that NEXTGEN TV is far enough off that having an external tuner (or some other identified solution to upgrading) probably isn't a big deal.
One issue that needs to be considered is how the DVR handles shows that are back-to-back on the same channel. Some require two tuners to insure you get all of both shows while others (i.e. TiVo) do not. I don't see this discussed often enough in reviews. Shows starting early or late and running long or short perhaps isn't the problem it once was, but it is still an issue (especially if you're saving money by using fixed timers rather than guide service).