It is yet a relatively young project, but already very capable of managing small to medium sites with its intuitive and comfortable interface.
Twostep's central idea is separation of concerns.
The creation of a website is divided into two distinct steps which do not only have very different requirements and environments, but which also aim at two different user groups.
Step 1 - Site Setup
A new website starts with the initial setup. Most of the popular CMS put great effort into integrating as many administrative details of this process as possible into their management interface. The interface gets cluttered, confusing and slow, is filled with administrative controls that aren't of any importance as soon as the site setup is done.
Even so, most management interfaces still do not reflect all required settings or details. The site developer has to constantly switch between the management interface and the CMS source code, internal and external templates, maybe even third party plugins. He has to spread his settings among the database and many different files and places.
Twostep, however, lets the site developer work with what he is used to. Code. Plain and easily extendable code files, separated and comprehensible templates. It offers the possibility to actually put the complete site setup into version control. The database contains nothing but content.
Twostep is good for developers.
Step 2 - Site Use
Since twostep leaves all the complicated and idle management stuff out of the management interface, there is not much that remains. Only things that make sense. Twostep's management interface is clean, coherent, fast - and beautiful. It unobtrusively overlays the actual website to change the content in place. It helps the user of the site to do what he actually wants to do - to put some content online, fast. To immediately see the effects of his changes. To be in control of the content.
Twostep is good for users.
Twostep has been heavily influenced by riotfamily, a very mature, powerful and intelligent CMS. If you have a Java enabled server with a lot of memory at your hands then you should definitely give it a try.