This is a fun tune. I don't know that many polkas, being more of a jig and reel girl myself. But there are a few fiddlers that make them sound so beautiful. I learned this polka off of a youtube video of Kevin Burke. The tune itself was written by Donàl Lunny. There are three parts to the tune, and the 2nd and 3rd parts have some jazzy syncopation to them.
When you hear a good polka by a Kerry fiddler for example, you can hear that nice swaying 1 AND 2 AND feel. If you watch Kevin Burke closely you can see he gives a pulse on the second half of the beat with his bow. To me I can see the connection between this type of pulsing bow and Old-Time music from the South which also features that extra Umph on the off-beat.
To see Kevin Burke play this tune in a set, go here: http://www.youtube.com/watch?v=_pOtZkeJkLE