I've recently switched back to using Subdreamer, and my experience has been positive. The company has been under new management since 2010, and they're very quick at fixing major problems. They've also made significant software improvements since I first stopped using them around 2007. Tobias really went out of his way to help me get situated.
So far as using Subdreamer, it all depends on what you need. It doesn't feel as modern as WordPress, and certainly isn't as simple, but my experience has been it is a lot easier to expand than WordPress. Just as an example, you want to add a new widget (plugin) to your sidebar. To do this in WordPress, you need to edit the functions.php file, edit the sidebar.php file, etc. Adding a new widget area in Subdreamer (called a plugin area), one edits a single template file adding:
HTML:
<plugin>
<div class="plugin">
<plugin_name><h3>[PLUGIN_NAME]</h3></plugin_name>
[PLUGIN]
</div>
</plugin>
This is taken straight from my theme, and in reality all you really need is <plugin>[PLUGIN]</plugin>. It's all just self-explanatory template variables.
You're also not going to find any other, or at least I haven't, fully-featured CMS that integrates as closely as Subdreamer does with Xenforo. To correct a misconception earlier in this thread, when you integrate Subdreamer with Xenforo the Xenforo database is used for all user account management. You can have a separate XF and SD database so long as the SD database user has access to your XF database. You can map primary XF usergroups to Subdreamer usergroups to, say, create content specifically for staff/paid members/etc.
Just as a final statement, this is all just my opinion. If you want to see a live example PC me and I'll send you a link to my site.