The Griffin iTrip SE was pretty much unusable. The transmission is incredibly quiet - so quiet, that even at high volumes, you still struggle to hear it. To add to insult, it turns itself off every so often due to "power saving functionality". If it's a European model, things are made difficult still with a feature to deter pirate radio stations by selecting a random frequency every time the device is turned on. Sadly, it makes life worse for the majority that use it for good and I'd hardly say it deters pirate radio stations (although why use it if it only has a weak signal anyway?).
There can be good things said about the wide compatibility of iPods that it can connect to and the ability to still use the headphone jack whilst transmitting is an added bonus. However, if you appreciate music (and by that, I mean listen), you should avoid it completely.