I was confused by a lot of things when I first found out about the wowace transition. Since then I have gone on a fact-finding mission to try and understand what site is what, where do I go and what do I do. A lot of this might be completely obvious to a lot of people, but for me it was an entirely new territorry and therefore I hope this post will be of use.
1. What's the relationship between WoWAce, Curseforge and Curse?
WoWAce and Curseforge are intended to be sites for developers, to provide them with the tools they need to maintain their projects. They are not directly intended to be used by end-users.
Curse on the other hand is intended to be the portal site for end-users where they can get the fruits of the addon authors' labours.
WoWAce and Curseforge are intended to represent two distinct author communities, with their own culture. They now share a lot of the same software, but maintain their own unique features and flavours.
An important feature of both WoWAce and Curseforge is that a project that is maintained on either one of them can automatically gets pushed to Curse for end-user consumption. Any project details filled in on a project page on either site can automatically appear on Curse.
Think of the whole thing like soft drinks: both Coke and Pepsi have their own factories, which consumers don't need to worry about, and both are sold through the same retail outlet, namely your local shop.
3a. As an author, what happened to my project that was formerly hosted on WoWAce?
The former SVN tree was imported and split up into separate projects under the new WoWAce site. Lot of the imported projects were successfully attributed to their owners. However, lot of them appear as being owned by "wowaceSVN". If that is the case, in order to gain control of a project, you need to claim ownership over it with your WoWAce account. In most cases you do not need to create a new project.
3b. As an author, what happened to my project that was formerly hosted on Curse.com?
All projects were imported to Curseforge. From what I understand, you can no longer directly upload files to curse.com.
4. As a user, where should I get my addons from?
The best thing is to get your addons from Curse. Things are still in a transitionary period, but eventually both Curseforge and WoWAce hosted addons will appear on Curse for downloading.
5. How are author account details getting merged between WoWAce and Curseforge?
I don't have certain details on this, but from what I uderstand, the staff are doing everything they can to merge your WoWAce and Curseforge accounts. In my case I found that I didn't have a WoWAce or Curseforge author account before, but had a working Curse account. That seemed to have been imported to both. The staff are very helpful in manually helping with any account merging issues that arise.
6. What's happening to files.wowace.com and WoW Ace Updater?
These are discontinued. The old wowace SVN still exists in a "frozen" state and packaged addons are still available on files.wowace.com for a short period, and WAU still works and will do so for a short period of time, but will disappear very soon. That's the whole idea. End-users who were relying on WAU to get their addons updated will no longer be able to do so. The idea is to remove end-users' direct access as much as possible from WoWAce, and instead retain it as an author community.
7. So what are my new options?
Your recommended options are to download addons manually from Curse, or to use the CurseClient software for automatic downloading and updating of your addons. The CurseClient is still work in progress, but is the intended end-user tool for addon downloading.
You can also download files directly from a project's WoWAce or Curseforge page, but you are likely to encounter more technical mumbo jumbo than you need.