I have had a cake very similar to this but along with the guinness you can raspberry liquer...Oh so good.
If it's anything like these Guinness cupcakes...http://www.bigcitylittlekitchen.com/2007/07/06/beer-cupcakes/
...I bet it's fantastic.
I will definitely be trying one or both of these recipes in the near future. I wish I had thought of this when I bottled my Dry Irish Stout last week and had a bit over a cup left over...