There has been lots of confusion over this ielts issue, and its been overflogged many times over. The problem stems from the fact that folks base their judgement on what Mr XYZ did 2months ago, without having a clear background info about Mr. XYZ.
I made a written submission, but that was because i only needed 4points under the language proficiency to qualify, and i didn't see the need to go write a test just to make 4points out of a possible 16/24. Mine was ok, and i'm expecting my Passports from Accra anytime from now, but i don't know how many points they awarded based on my write-up. Doing the test would have pushed me to 80points which wouldn't be of any additional use to my application. I would have written the test if i'd needed 16points to make the passmark, cos there are no guarantees with written submissions - Immigration officers are not trained language proficiency assessors, and you could have 3 different caseworkers awarding 3 different marks for the same write-up.
I have looked into the language assessment handbook they use, and its a massive book nubering hundreds of pages, certainly its not what they'd be happy to do all the time.
In a nutshell, if you need max points under the language proficiency - its wise to do the ielts; if its just say 4points - there are better chances of scaling through with a written submission. Every case is treated on its own merit. A written submission of an Accountant with ExxonMobil may not be awarded similar points with that of another Accountant working for Ogo-oluwa Nigeria Enterprises.