As I stumbled only over the most unpractical solutions when running into this problem once more, I decided to share this on with the public.
Here is the easiest way to get a URL (also SEF, depends on your settings) from an Article/Item ID.
I currently did this in Joomla 3.2.2. You can use this for example in the template override for the blog view.
$item = $this->item;
$link = new JURI('index.php?view=article&id='.$item->id.'&catid='.$item->catid);
$itemUrl = JRoute::_($link);
Please help sharing this one.