Ah, for hunting for new stations, the Zinwell has a manual scan feature. You can sequence through all the channels similar to the manual search in Zenith, but it is not nearly as handy as the Zenith. With the Zat, if you spot something, it doesn't seem to add it until I do the 'search.' I often see momentary blips in manual search, but that's not enough to pick up the search. But last weekend I saw a really badly broken up picture of a (duplicate) PBS station 50 miles away, with Terk HDTVa in the attic aimed in the opposite direction. So it was impressive to get it at all, but for station exploration, I prefer the Zenith, which also lets you just enter the channel from the keypad.
Adding--although you don't want to add the channel, there seems to be some sort of stabilization of the picture that kicks in when it's an official channel on the list. Other people here refer to it as a learning function, it's like the box gets used to the signal variation and compensates. There really does appear to be something to that, like it settles in and gets better at locking onto the signal without pixelation. I've never given it much time in the manual scan mode, but it does seem to show the picture more easily once it's on the channel list.