To answer your subject question, yes, we use s2member and are very satisfied with it. We've found the community support to be very good in responding.
Regarding your second question -- you describe adding members to your site, and then ask about listing businesses in different categories....
If by "businesses" you mean posts, and categories are actually wordpress categories, then the typical WordPress category.php and single.php theme pages address this.
If by "businesses" you mean S2members, and by categories you mean member levels (?), then it sounds like you're describing a member directory.
I don't know if s2member provides a directory system as part of its built-in functionality, but we've been able to implement this ourselves by creating a page to list members, and another one to list a single member's details.
Member directory functionality is also possible by adding a member directory plugin. I'm about to consider "Members List" for our project as it looks promising.