My first site was created with Mambo. If you use that portal, make sure to get Xaneon Extensions which creates SEO Friendly URLS.
It was alright, but I found it a chore to publish information from a database onto the page. I had to write my own custom modules and components in php to do some of that.
If you are looking to add content (not from a database) and banners / links – it’s great. It is very easy to do such things once you know your way around the CMS.
My second site I created from scratch. I had a lot more control over all aspects of SEO that way.
kw