I've been searching the net for a solution.
My problem is that the info window's height is not calculated properly. There are no images in there so it is not an issue with the image loading later and the size is not known when the bubble is created.
Also if I fill it up with about 15 lines more text the size is starting to get alright.
This is what I feed to infoWindowHtml:
<div><h2><a href="">Some title</a></h2><dl><dt>Location:</dt><dd>london</dd><dt>Description</dt><dd><p>Example text </p></dd></dl><p><a href="">Read more...</a></p></div>