Bought this for my daughter's birthday in combination with a Nano 4G, having already read glowing recommendations for it. I'm familiar with pro and high-end home and car audio equipment, so I have quite high standards already. Obviously, as a small plastic lump, it was never going to match the standards of "real" equipment, but this little piggy really surprised me with its solidity, the quality and usability of the remote and the sound quality emanating from its eyes, ears and fat little tummy - I was expecting more pork-wality from something so small and toy-like.
If it's lacking anything, it's high-end "airiness", but as a package, it's highly recommended. Despite its diminutive size, it's not lacking grunt in the bass - it plays within its capabilities, without any of the over-emphasized boom-box effect. A separate bass level control allows for some adjustment of the "subwoofer".
It comes with a selection of dock adaptors but does not include one specifically for the Nano 4G; nor does Apple's adaptor fit its mounting points. This isn't a problem - the Nano sits nicely in one of the larger dock adaptors, supported solely by the dock connector. Just make sure nothing hits the exposed iPod (pillow fights?) and you should be fine. I might use my Dremel (Dremel Rotary Tool 300 Series + 25 Accessories
) to fit Apple's adaptor into one of the pig's supplied adaptors if I can be bothered.
In summary, don't be concerned about the novelty aspect suggesting toy-like quality - snout to worry about.