Yes, you can use it to watch DVDs without cable hook up. I have it set up in my workout room and I only use it for fitness DVDs. Great sound and picture. You can also use a Chromecast device or ROKU if you want to stream. It's the the way to go and save yourself lots of $$$.
I have 3 of these in various demanding locations (employee training) They loop play for what is essentially 24 hours a day. 2 of the three have been at it for almost a year, the 3rd about 5 months. No problems.
I bought the smaller insignia combo TV and so far it has been great i think with the new technology they have a better track record than the old combos
We use it in our camper and are unable to find local channels without connecting it to our external antenna. Once it's connected, it picks up everything in the area.
You need to have an HD antenna to pick up the HD stations. I have found that this unit will not "find" any stations without one. Talk to a Blue Shirt at the store to make sure you get a decent antenna. Different things affect the signal, like living in the flight zone of an airport.