I have a telephone and a pair of stereo headphones made by Coby. Both work very well; in fact, I've had compliments on the transmit audio quality of the phone. (I'm not using the phone at the present time, as it does not have caller ID.) The headphones sound excellent with my Aiwa bookshelf stereo system; as a matter of fact, these phones sound much, much better (better overall frequency response) than the Sony MDR-24 stereo phones they replaced several months ago. I wouldn't dream of comparing the Coby phones with, say, Koss or Sennheiser headphones (there is probably no comparing them to these high-end phones anyway), but the Coby headphones sound excellent in their own right as far as I am concerned. The only thing I could find wrong with my Coby stereo phones when they arrived here from Radio Shack (I had ordered them online) was that the plastic piece which fits over the stereo-mono switch was missing. However, I didn't notice that until I'd had the phones a month or so. Since it doesn't affect the sound of the headphones, I didn't bother sending the phones back to RS.
I can't imagine why RadioTVNut in Mississippi doesn't like Coby equipment, unless he has had bad experiences with it.
As I said, I've only had experience with two pieces of Coby gear; I don't know about their DVD players and other equipment. Perhaps that's what he is referring to--maybe Coby's DVD players are made with such flimsy, cheap plastic parts that they break within a month (!) of initial purchase of the device.
My own "stay away from" off-brand of electronics (one of them, anyhow) is GPX. As I mentioned in another post, I had a GPX radio/cassette recorder about 25 years ago in which the cassette deck failed within three weeks after I bought the device. I didn't take it back to the store, although I could have (probably should have), as the store from which I purchased it was only a block or so from my home at the time.
However, I made up my mind after that experience that I would think at least twice before ever again buying any piece of electronic gear bearing the GPX logo. I saw a GPX DVD player in an ad flyer for Target in my Sunday paper last week; the player was selling for something like $15. I can just about guess how long one of these players will last. It's probably made with flimsy, thin plastic parts, the cheapest electronic components available, and may, for all I know, have a non-resettable timer in it set to disable the thing after X number of hours (!), days, weeks or months after initial purchase, this being a hint (a very strong one) to the owner that the unit will fail soon and will have to be replaced.
I realize nothing lasts forever, but sheeesh--this is ridiculous. It wasn't so long ago one could buy a TV set, for example, and expect it to last 10-20 years; in fact, I had two Zenith color portables that were at least that old when I got rid of them 10 years ago, and they were working as well as they did when they were new. These days, one can purchase a small-screen flat-panel TV for under $200, but he or she had better not expect the set to last anywhere near 20 years; more likely, the set will fail within a year or two if it's an obscure offshore brand, but that's the way it is in the 21st century, like it or not. LCD flat-panels need a backlight to brighten the picture enough to be watchable; these bulbs cost some $200, more than many small FPs sell for, so I predict in a few years, or perhaps even sooner, we will see a lot of FPs (those that aren't being recycled, anyway) on curbs and treelawns with nothing more serious wrong with them than a burned-out backlight. There will as well be a fair number of FPs thrown out when the video driver ICs go bad, as these are molded into the cable between the panel and the chassis.
And so it goes.