Just installed the ATV app, and the 1st thing I noticed was that it is FAST and SMOOTH! Such an improvement over every other streaming device Tablo app I've used (FireTV, Roku). I've watched a few different channels, and have had zero buffering. FF/Rew is super quick and fluid. I very rarely use voice control in general, but even a quick check of "go back 30 seconds" worked perfectly.
You are looking at a pretty sizable investment to get started, but of course, you are paid back in a handful of months by forgoing cable/satellite bills. Also, I am sure most people already have at least some of the needed hardware. When I set up my system, I believe I spent about $400 or so. Considering I've had it for ~20 months now, I've saved ~$2,000 in DirecTV charges, so no complaints whatsoever. The new ATV app completes the circle.
Here are the startup costs:
1) Tablo 4-tuner ($300) or 2-tuner ($200)
2) USB HD (~$60) (Tablo has specific recommendations, so assume you need to buy a new one)
3) OTA antenna ($40-$150+) (this is very much based on what you need for your specific installation)
4) Coax cable ($0-$100) (again, depends on your situation, you may not need any new wiring)
5) AppleTV(s) ($150/ea) (often on sale for $125, and you can use other streaming devices if you want, although seeing the performance of the new ATV app, don't skimp!)
6) Programming guide is $5/mo or $150 lifetime (and, unlike TiVo, the lifetime is on your account, not on the specific Tablo box, so you can replace the box and/or add additional boxes and still have lifetime guide service) (note: technically the programming guide is not mandatory, but you would lose a ton of functionality by not having it)
Tablos are pretty readily available on eBay. My cousin just bought a 2-tuner box last week for $120, including a 2tb external HD and shipping, so saved ~$140 off of new.
This finally makes Tablo something I'd recommend. In the past, I would always give 100 different gotchas to people that asked about my setup.