Hello everyone - I develop this simple app https://marketplace.atlassian.com/apps/1217709 (Project properties for Jira) that takes care most of the above requirements. Please give a try and feedback to me if it helps.

Yes, I noticed the experimental REST API features for this as well.  

Is this an indicator that this feature will be implemented in the future?

There's an experimental REST api for this in current JIRA.

Thanks for everyone's feedback and votes.

We've taken a look and we've decided that we won't be implementing this feature in the near future. We will likely tackle the issue of project summary reporting in a different way.

Please note that votes is one of the determining factors that we use to plan our roadmaps, for a full description please read our blog post: https://answers.atlassian.com/questions/110373/how-does-the-jira-team-use-jira-atlassian-com.

We hope you understand and appreciate our honesty on these requests.

Thanks,
Otto Ruettinger
oruettinger @ atlassian dot com

There are so many possibilities for project specific fields: project synopsis, project current status, project special notes all providing the ability for us to role up a high level current project status report. Upper management does not want to wade through the issue details but they do want to know a description of current project status. All of this could provide new functionality and opportunities for Jira within our organization. Architects, directors, vice-presidents, etc. do not use Jira because there is too much detail for them but if project level updates and status were available they would live in Jira....Hello? You are missing a big opportunity to influence those people who can make things happen.

Almost 8 years now... Still not resolved. I can understand that there is a severe need for this feature but why have you not resolved this yet?

I found this plugin https://plugins.atlassian.com/plugin/details/35576
Although there is no support, documentation or screenshots. Lets hope the author of this plugin improvises on it soon.

Another potential use for custom project properties:

We have implemented custom Jira reports. Different types of projects have different sets of reports that make sense for them. (For example, if it's a project for an external customer vs. a core development project).

Right now, it's difficult to have different reports accessible from different projects. If the reporting plugin could query a project property, however, it could dynamically determine the appropriate set of reports that should be made available.

Our company would benefit from having custom project properties, particularly if we could use these properties in the work conditions.

Some of our project teams use Crucible code reviews, for example, while others do not (shame on them!). For the ones that use code reviews, we've added the workflow condition that prevents resolving an issue until all related change sets are part of a code review.

Right now, we have two virtually identical workflows: one that has the code review condition and one that doesn't. It'd be nice to be able to use the same workflow and use a custom property that controls whether or not it comes into play.

I haven't tested this but this plugin appears to provide custom project properties:
http://confluence.atlassian.com/display/JIRAEXT/Insight+JIRA+Project+Portfolio+Management+Plugin

Project level custom fields would be very useful, especially if they could be accessed from workflow post conditions.

I would like to use project custom fields this so that on some special transitions, I can automatically assign the task to a particular user for that project.

You can add post conditions to transitions that assign to the reporter or project lead, but I would like the ability to nominate another role on the project (or more likely using the "Update Issue Field" option to set the asignee)

This would be used in a consulting environment where tasks need to be assigned to the project manager at our client on particular transitions (and back to our project manager on other transitions. This is possible at the moment, but is done using post conditions in the workflow specific to that project. Ideally, I would like to reuse the same workflow across multiple projects for multiple clients.

In the 'standard' workflow, I would then define a post condition that assigned the task to the custom field in the project - I assume this would require changes in this component as well...

Perhaps there are other ways of achieving this?