I had this issue before but came up with a temporary fix for it, but its rearing its ugly head.
The Next Page and Previous Page links in paginated pages don't have a div class to them and can't be styled.
I've tried setting up a new page.php and adding:
<div class="navigation"><p><?php posts_nav_link(); ?></p></div>
All that did was give me two sets of the links. Looking closer, it appears that they are created dynamically inside of the_content(). I checked inside marketpress.php and it looks like it uses get_posts_nav_link() to create the links. Would it be possible to create a snippet to place into functions.php that will wrap get_posts_nav_link() and/or posts_nav_link() in a div tag?
Getting it to where some styles can be applied to those links would be extremely useful in streamlining navigation. Right now, they just come up as dynamically created page content with a <p> tag around them. Adding CSS rules to them will effect the entire site. Everything else in MP is pretty well divided up with classes and id's, that navigation spot is an important one that feels like it was overlooked. I'd even vote to have this added in a future version.
Any help on this would be much appreciated.