CAML can be rather hairy, and it took me some digging to find out how to query a list for items assigned to a user (of the “User” type). It turns out the best method to do that is to query by the user profile id. This will pull you back items for just that specific user.
<where>
<eq>
<fieldref name=”PersonFieldName” LookupId=”TRUE”/>
<value type=”int”>UserID</value>
</eq>
</where>