Ok, so the AA flickering issue and the thing I noticed...
After looking closely at the flickering states when AA is enabled in VP9_DX9 (via general preferences or specific to the table) or forced in the nVidia control panel then pausing to assess, I can see that one of the apparent two images being displayed / alternated is being done so with what appears to be incorrect transparency settings and / or ordering issues (as can be seen through what should be transparent sections and also the edges of the lower plastics that were highlighted earlier in this thread while dealing / providing bug reports for the ordering issues.
Here is a screen shot of both states of the table in what appears to be why it's flickering in that the images are actually changing in the regard above:
First, what looks normal:
Capture of Centaur WIP (60b) during AA flickering Issues (Image in normal rendered state of flickering - alternating).PNG 1.47MB
16 downloads
Now the captured "flickered" / non-transparent and / or incorrectly ordered stage:
Capture of Centaur WIP (60b) during AA flickering Issues (Image is altered not just flickering and appearing non-transparent).PNG 1.46MB
16 downloads
These were captured in one running of the table just using the escape key at the right times.
The ball is still another deal it would seem and also the bottom of the base / heals of the flippers as lines appear through them when they're rotated with AA enabled. I've tried turning off the ball anti-aliasing, which also disabled the ball transparency at least in previous DX7 builds, as well as ball decals, and even tried setting the ball image to a solid green square texture using a .bmp file and it always still flickers. So, it doesn't seem to be just transparent related solely and as far as the ball at least something else must be going on in the code. However, I'm hoping the find that the flickered image is actually not correctly ordered / transparent may provide some food for thought or an idea of things to check.
By the way and a side note, at the moment it appears ball decals are not working / showing in the latest VP9_DX9_test7 build nor any previous version.
Further to these findings on the AA flickering issue, while testing and verifying the above, I tried to replace the transparent ramp for the plastics layer with a flasher object instead (just for the hell of it). It yielded two interesting findings, first it appeared to not be affected by the flickering issue with AA enabled and maybe the flasher object could be investigated at a code level and compared to the ramp objects as to why the former seems to work better around this blinking issue. Second, a new problem arose where there appears to be an issue with a flasher object (at least without additive alpha enabled) when placed above a ramp with additive alpha enabled. In the Centaur WIP I had the plastics layer as a static test "flasher" at 55.8 and the additive alpha gi ramp objects below it at 52.8 were shining / affecting the top of the plastic instead of only the areas beneath (i.e. not ordered correctly). This was not dependant on AA or any other setting and would not yield the same issue (worked correctly) when ran in the VP921rev930 build. So, that seems to be a new / isolated incident on it's own.
However, if I replaced / tested an additive alpha gi ramp section with a flasher object instead, at the same lower height I could get the whole area to be blink free with AA enabled and display correctly. BUT, and here's where it gets really weird, I would have to actually set the flasher object test additive alpha gi object - that is lower (52.8) - to be drawn "in front" of the higher set 55.8 transparent plastics "flasher" object, which is totally opposite to what one would expect to get the lights drawn under the transparent plastic. I will send a link to the table where I've done these changes to you mukuste in a PM so you can check out. Here is a screen shot of the pseudo fixed but weird flasher object for plastics images work-around / test - note the lower-mid right plastic by the launch lane displaying the additive alpha gi flasher object correctly but this is only when it was set to draw in front:
Capture of Centaur WIP (60b) with AA flickering Issues somewhat resolved by changing ramp to flash object but new problems with ordering of Additive Alpha GI ramp underneath (highlighted).PNG 1.48MB
16 downloads
What this also means through these tests is that even in the current build of test7, I can actually alter the behaviour of the rendering still by using the draw in front / back options for the flasher object so there's something with that (at least when it's got the additive alpha options set and / or in the combination of factors as in the test table / scenario).
I've got a test table and some screen captures to focus on the higher flasher object over a lower additive gi alpha ramp issue that works in DX7 but not in DX9 (no AA related) and will post those and the test table in a follow-up post - this ones getting long / full again 
Maybe between Toxie and you mukuste this may be of some assistance. FXAA looks pretty good and doesn't seem to be as blurry as in VP921 (if the OS / driver version combination supports it). However, aside from the flickering, AA in these DX9 builds looks wicked and really smooths out all objects making the table just that much more realistic looking. FXAA still doesn't smooth some parts as well (whether forced in nVidia control panel or using the built-in quality mode). It would be great to get real AA (MS or CS modes) to work blink free as that would really bring this process to a great level in that arguably a holy grail of VP9 was that of actual supported AA finally working (no black lines, no bad edges on dynamic objects / drop walls, etc.).
Thanks again for bringing this to the point it already is and options we currently have.