1. Create a new issue ==> Create Issue dialog box appears
2. Enter information into dialog, including into several custom fields
3. Make sure "Create another" checkbox is checked
4. Click "Create"

Expected: A new Create Issue dialog box appears with many fields already containing the information previously entered
Actual: The new Create Issue dialog box appears but it is not retaining any information from the issue just created. The new dialog box is as empty as the first one was.

We often enter a a lot of items at one time. Having the values in various fields automatically filled in has been extremely helpful. This was actually a BIG selling point for us to use Jira at all for task tracking.

Suddenly not having this happen has made creating items a lot more of a pain for us.

I assume that this long-existing functionality has been removed because some folks don't want the fields auto-filled. But presumably they'd be entering other data into (most of) those fields anyway. So if they already have data in them that doesn't make much of a practical difference to the "don't auto-fill" folks.
But to those of us "DO auto-fill" folks, particularly those that have a lot of custom fields, it's a VERY big deal.

I realize it's impossible to keep everyone happy, especially when they want opposite things. But you could get very close if you make auto-filling another of the General Configuration settings like all the others on the System Settings page (https://[instance]/secure/admin/EditApplicationProperties!default.jspa).