This little mic works a treat. It plugs into the iPod Touch even when the Touch is in the case I bought for it (http://www.amazon.co.uk/gp/product/B002V872WS/ref=oss_product) and (so far) appears rugged enough to be left in situ even when the Touch is wrapped up in its bed.
Performance is entirely satisfactory for such a low cost mic. Skype calls are clear.
Some have complained that when the mic is inserted, the internal speaker doesn't work. It's perfectly normal that whenever something is plugged into a headphone/mic jack, the internal speaker/mic is disabled. How else could external headphones be useful? So it is with the iPod Touch. Apple, however, provides the app designer with a solution to this, namely the facility to turn the internal circuitry back ON. So far as I know, Apple is the only company to permit this, to it's hats off to Apple again for great design.
With this mic inserted, and the Skype app running, you simply tap the Speaker button provided within Skype and bingo! the mic works AND the speaker works. If other apps don't do this, write to the app developer and complain. The mic company can't fix the issue.