True, Milestone is not officialy supported by CM team. But kabaldan is following cyanogen and respecting their changes (naming, version numbering...) with necessary adaptations for Milestone (otherwise it would not work (different radio, kernel...)).
I guess the reason for missing "RC1" in file name, "about phone" or similiar is because this device is not officialy supported and they do not define buildype for non-official releases, just UNOFFICIAL. However, I could be wrong and the RC1 does not apply here. (however, latest update is functional and running smooth on my device. the changelog might me messed up. I appologise if it is incorrect (I know it is highly incomplete.)
btw, it seems that kfazz over at Droid section is doing quite well in making CM9. Seeing they have unlocked device they now have all the proper files for the GPU to be fully functional on ics. We have locked device and the only way to get that kind of update is by kernel module. I assume this is extremely difficult to acomplish.
Regarding nightlies - other things that have been ignored for too long need to be attended. The primary reason why I accuired hosting space. Anyway, it's a very long story.
And files that were there (updates to cm7 & cm9) are mostly gone. CM7 completly because kabaldan released release version so I see no need for old files and cm9 has only the most recent updates (June 17. and 27.) plus new gapps (June fifth). These will eventualy go as well (no rush for now) but you'd might want to make backup, just in case.
The device shall stay with me, possibly even after "death". it is extremly good piece of work. If only Moronola hasn't screwed us up...