A few of my apps utilize the built in custom profile fields to manage user data.  In 3.x, the unique key ensured we got data from one field, and one field only.  In 4.x, there is no unique key for custom profile fields.  There is no way to ensure the field you're calling is the one with the data you're expecting.  Custom fields are a great functionality, however there is no way to limit the client from creating more than one field of your custom type.  So while custom fields help a great deal, there is still no guarantee that it is unique.  

Is there any way we can get a unique key re-added for profile fields to simplify the process of locating a custom field with the data in it we're looking for?  Or add a flag on custom fields to only allow the creation of X fields of that type?

If not, do y'all see another way to go about this such that the above can be achieved using the existing structure?

+1 for this post. I have multiple clients that make use of profile fields, and I've done a lot of customization based on specific fields. I can't even begin to fathom how I would do an upgrade properly without being able to use the key. The only thing I can think of is creating a whole bunch of useless system settings to identify fields that I should be able to identify programmatically.  

Not at the moment, but it is on our list of things to improve.

Any word on this improvement?  It's been a year and a half already.

15 hours ago, Aiwa said:

Any word on this improvement?  It's been a year and a half already.

Not yet