Residency Application (Stamp 4) - Spouse of an Irish N.U.?

According to this link:

http://www.migrantproject.ie/documents/ ... 11_002.pdf

You should go to the GNIB and ask for Stamp 4 residency which allows you to live and work in Ireland based on your marriage.

GNIB may tell you to make this application through the Spouse of an Irish National Unit at the Irish Naturalisation and Immigration Service (INIS) in Dublin. The processing time for residency applications can be up to 12 months.

In practice, does this ever happen? Or do most people get their Stamp 4 on the spot?

How do they decide whether or not to give you Stamp 4, or refer you to the the Spouse of an Irish National Unit?

Does the country of origin play a role? Say, if you're from the United States vs a third-world country?

Thanks

Dan

not from personal experience, but my colleague got stamp 4 at GNIB burgh quay on the spot. They are married, have two kids together and have been sharing home for ages.