OTA only.
We still have cable and a Bolt (not enough votes to cut the cord) and I had been using Windows Media Center to provide extra tuners in case of conflicts. A year ago I bought a dual tuner Tablo to fill that role and my experience has been very good. I have had no need for reboots, and updates and new features have been rolled out at a decent rate. It does not provide the trick play capabilities of a TiVo, or Wishlists (although automatic channel skip, still in beta, works decently), but for basic DVR service it has been fine. Without a subscription you get only 24 hours of guide with time and channel recording. Service is $5/mo, $50/yr and $150 for lifetime. The subscriptions are for one device on your account so upgrading to a newer device requires de-registering the old box. Tablo is rolling out 14 day grid guides but they have icon-based presentation of shows by channel, TV, movies, sports and prime time.
Their newest device, the Quad, is the first to allow installation of an internal HD, if neatness counts -- it did for me so I went with a Dual with 64 gigs of memory built in. You can set recording and live TV for anything from 1080p/720p 60fps 10 Mbps on down. My old eyes are happy at 720p 3 Mbps so 64 gigs is plenty for me, especially since it is simple (with user-written software) to back up or archive to a networked drive. You cannot, however, use the Tablo to play back those files but other apps/channels will do so. My Roku Streaming Stick+ works very well, my Fire TV devices only so-so.
Everything written to the HD, even the live TV buffer, is transcoded to Mpeg4 so tuning to a new live channel will result in a four to five second delay. Because of this approach, you can stream to up to six devices at a time though only two (or four) can be live TV. You can use a browser to use the Tablo as well as phone and tablet apps that allow you as much control as the browser to schedule and manage recordings.
Somewhat on a whim, I picked up a dual tuner Fire TV Recast (as a Prime Member it was only $130 with life time included). I do have a problem with it -- my PBS station on VHF 8 does not come in reliably. That seems peculiar to that station and the Recast as my Windows MCE, Tablo, and TVs have zero problems with VHF 8 no matter what sort of antenna I use. If you are in the Amazon system or willing to commit to it (Recasts do not work with Roku, Apple TV, nVidia Shield, etc., while Tablos do) you might consider that. It has different limitations given how it works. While it records the original ATSC signal it transcodes to 1440x720 on playback and can only handle two viewing devices at the same time, whether live or recorded play back. Basically, you must use your TV and Fire TV device to do anything. There is no browser access and phone/tablet access are too basic to be useful. The Recast does integrate completely into Fire TV devices so there is no need to wait while an app loads. Only one Recast per Amazon account, though.