Ello,
I'm currently using a tool called Expression Engine (
ExpressionEngine - Publish Your Universe!) - and while it's more of a blogging tool than a full-blown CMS, I'm finding it REALLY (yes, in capital letters) powerful and it's managed to do everything I need and more so far. It depends on the type of site you're creating but if it involves a mixture of static pages and things like news, events, blog entries, etc, then it's definitely worth a try.
I've always found things like Mambo, Joomla, Plone really restrictive in terms of design, or at least really complex to apply the design and layout you want. With EE you kind of do it the other way about, starting from a blank canvas and inserting tags where you want the content to appear. For me it's a really good way to work.
Good luck!
J