Ofcourse you will run into the inevitable bugs and issues. For those I point you to the Ace3 Jira: http://jira.wowace.com/browse/ACE
Try and be as clear as possible in your bugreports/suggestions, preferably with added simple code that shows your problem/issue.
Do not release any addons using the Ace3 Alpha to the public. It's ok to develop them in branches, Ace3 is not ready for public releases yet.
We will be working dilligently on the remaining issues for a Beta release.
I made a small notepad-like addon using Ace3. Code is attached. It's not quite finished. It was mostly to experiment with AceGUI but it does use a few other libs like AceAddon (including modules), AceDB, and AceConsole.
Of most interest may be that I implemented a custom widget: A multi-line edit box. I hope you will take a look at it and consider including it in the core AceGUI. Multi-line edit is something I think has been sadly missing from all frameworks so far. It was rather frustrating getting it to work. Not because of AceGUI, but because Blizzard's support for putting a multi-line EditBox into a ScrollFrame is.. hmm.. well.. it could work better. But I think I've got it working pretty well - though I bet patch 2.3 will require some changes.
I'm thinking that a lot of custom (but still common-ish) widgets could be added to a separate library, e.g. "AceGUI-Extras". Itemlink buttons would certainly be one such widget. A multiline edit.... well at the very least it would go into that lib. But maybe even the core AceGUI lib; I'd like to take a quick inventory of how many addons could benefit from it. One core tenet that we try to keep with Ace3 is that a majority of addons should (potentially) benefit from adding a feature to an existing library, to avoid bloating core libraries with features only used by few addons.
(Though to counter rigidity we do like to make things extensible, for example with custom controls)
In my opinion multi-line edit belongs in any core GUI library (wether in WoW or elsewhere). The only reason one might consider not having it is simply that Blizzard's implementation of it sucks tbh - so it's may not ever work fully as one might expect. There are some changes in patch 2.3 that might improve this. But it could also be worse. :(
Multiline edit is one of the controls that i've been wanting to write to have in the core, but have been putting off since edit boxes are one of the more annoying GUI elements to work with.
One can hope patch 2.3 makes them a bit easier to work with. I'm thinking about the new methods to both get and set the cursor position. That should remove the need for some nasty hacks we currently have to use.