Gherkin syntax files are just plain text so any editor such as notepad can be used. However, one of the more important things we are using this for is to provide tables of sample data. Without good formatting options the files become hard to read.
There are some good tools (see: How to get Gherkin syntax highlighting for .feature files in Visual Studio?) for visual studio such as specflow.org or https://github.com/henritersteeg/cuke4vs. Another option for developers using eclipse is discussed at Cucumber IDE for feature writing with autocomplete? However I don't want to require it be installed for our business analysts.
Here is a syntax highlighter files (http://productive.me/develop/cucumbergherkin-syntax-highlighting-for-notepad/) that can be imported into notepad++ but it does nothing for table formatting.
Are there any other options that I might have missed for allowing non-developers to efficiently edit .feature gherkin files?
There seems to be a couple of projects in the works.
Neither really substitutes for a conversation with your business domain experts.
There is an updated eclipse plugin called xgherkins at github for eclipse users
A good solution for this is to use the Behave plugin for JIRA.
In a good SCRUM team, your domain experts and business owners should define the backlog and describe what they want. It is awesome that you can then immediately add the Given/When/Then definitions for test scenario's.
JBehave also supports getting the .feature files from Google Docs. There is no syntax highlighting plugin for google docs though, so this only takes care of the synchronization problem.
I found http://www.bddeditor.com Seems fine for initial phase (they say "BDD Editor is work in progress".
If you are using JIRA you can try a plugin called Markin at https://marketplace.atlassian.com/plugins/com.fulstech.jira-gherkin-custom-field/server/overview. It supports both Gherkin and Markdown at the same time, so it is very useful for non-developers.
Disclaimer: I am the creator of Markin.
Notepad++ can highlight Gherkin syntax - see http://productive.me/develop/cucumbergherkin-syntax-highlighting-for-notepad