Picture quality is gorgeous. Of course, it's recommended to use a PC with a good, dedicated graphics card, but I also tried a cheap notebook and that looked OK as well. Also, you would want to use an HDMI cable connection instead of an old-fashioned VGA cable.
The borders on the 46-inch Samsung TV screen are pretty much the same as on my main office monitor, a 24-inch Samsung. WGT just doesn't support widescreen at this point, but this doesn't spoil my appreciation of, say, Bethpage Black's eye-popping verdure. 
There used to be a time, a year ago or so, when the full-screen borders on WGT.com were an ugly colour that stood out too much, but it's fine the way it's been in recent months.
The lag wasn't greater or smaller than on my regular monitor. And, you can imagine how huge the shot meter is on a 46-inch screen; you might argue it makes it easier to "hit the ding". I couldn't really confirm that, but... the game is definitely playable and enjoyable for me on the big TV screen.