You can play with the demo app @ http://demo.locomotivecms.com/admin
Some features are not enabled in the demo mode.
http://pogodan.com/blog/2011/06/03/we-ve-switched-to-locomotive - blog post on why an organization switched from refinery, adva CMS, etc to LocomotiveCMS.
Things like CSS/JS editiing, custom themes, custom attributes for the CMS pages, custom models, etc are missing in refinery.
You can do everything within the site itself unlike refinery where I had to write lot of ruby code to achieve certain features.