A really basic question, but I've read a lot about not just using the default attributes set. What are the benefits (both the the customer and in the back end) of having multiple attribute sets by product type, apart from LH filters?
Attribute sets are actually very important. It's crucial for performance (especially the layered navigation) that your products only have attributes relevant to their type.
Here is a bit more reading about it: http://inchoo.net/magento/importance-of-planning-attribute-sets/