They can be fun cameras. But if you want traditionally "good" pix, you will find them very limiting, and something of better quality would be the way to go. A starter Minolta, Olympus, or Pentax (and sometimes a Canon or Nikon) can often be had for the $60 you would spend on that 10 cents worth of plastic you are talking about.
I think of it this way: I'd own the Diana if it was a $10 camera. But anything more, and I'd rather just get a 99 Cent Store point and shoot or a disposable.
FWIW, I have found three Canon Sureshot Zoom cameras in thrift shops, each $5 or under. They have pretty respectable lenses for the price, and give very good results if used carefully.