I got one for christmas, and it worked great at first, except for the annoying high-pitched whining noise coming from the speakers. After about 2 days a horizontal line of pixels on the screen died, so I sent it in for a replacement, noting both problems. Customer service was nice and I got a new one shortly. This one has much less of a whine, though I think the screen doesn't seem quite as clear as my first one.
As a system it's okay, but it certainly doesn't replace my SNES. I haven't used it much at all lately, because it's still clunky and a little uncomfortable to hold. I've been very tempted to pick up a RetroDuo Portable however, after Satoshi_Matrix's thorough positive review.