I have been a heavy Things users since the beginning, but there have always been certain features that I have found lacking, such as sub-projects and a distinction between areas of focus.
Omnifocus has had all necessary features since I can remember, so I finally decided to give it a go for real. All active projects and areas from Things have been migrated to Omnifocus, leaving the someday/maybe list for if/when I commit to using Omnifocus for a foreseeable future.
The one thing I will have to live without for a couple of days until I can commit, is buying the iPhone app. That means I will be using Evernote on the iPhone to capture actions and projects on the go.
I am really looking forward to be able to use sub-projects and see if that increases my productivity and peace of mind about large projects. Perspectives are also something I look forward too, since that means being able to focus on just work or personal, even though there are deadlines arising in both places. In Things, everything is meshed together and it is practically impossible to completely separate all focus areas. There is an option to disable an area of focus, but that is a too inconvenient workaround.