I bought the same TV from 1SAD last month at the same price. It's my first HD TV, so I'm not an authority or anything, but to me, it looks just as good as the HD TVs they have at the sports bars. I watched some of the Olympics in 1080i and it was amazing how sharp the picture was. Seeing every little speckle on a gymnasts uniform, for example. And the menus with the names and stats of the athletes were super sharp.
It can read the digital air signal, but you still have to buy an antenna to get the signal just like the old days. I bought a $10 one at Walmart, and can get 2 channels, sometimes 3 or 4, including NBC in HD. I live out in the boonies. In the city, I'm sure you'll get more channels with $10 RCA rabbit ears from Walmart.
My Comcast cable box is over 10 years old (the first model that had the info button and program guide), so the HD channels don't seem to work on it. If those channels are black now, despite showing "program info" and not showing the "please subscribe" stuff, then it's not your TV, it's the box. Getting an HDTV won't make those channels work. I called and am getting a new Comcast cable box so that I can see more HD on this TV.
Back to the TV, it's true what others said that it will take about 10 seconds to turn on. The LED changes color immediately though, so there's no excuse to keep hitting the power button. The ability to switch between TV, HDMI, and all the other inputs is straight forward. The coax input is divided by cable and antenna, and you have to go into the menu to switch between those. The Channel scan works well (in fact, this is the first thing you should do if you use basic cable or antenna), as well as the channel skip. With basic cable (no box; just the cord coming out of the wall), I picked up a decent amount of channels, some in HD, some duplicated in both HD and SD. I used the channel skip feature to avoid duplicates.
TL;DR It's a fine TV, with all the features you'd expect of a non-smart TV, but update your cable box if you want more HD.