OK, after wasting (investing?) a day at getting this to work to my satisfaction, here are my lessons. Some are probably obvious with hindsight and a lot of my time was learning how to work the insufferable OS X (I now don't totally hate it any more!). Suffice to say that the Getting Started Paragraph in the Ejecta instructions page is VERY important.... LOL!
hollowthreat, I thought iAd implementation was pretty straight forward (once I'd figured out that I had to follow the instructions exactly). After enabling iAds in iTunes Connect, I just added a sub event in C2 on start of layout - Ejecta show iAd at bottom / top. And that's it - no massive and confusing codes to copy/paste! I did not use the 0plus1 plugin or the Ejecta Kitchen files. As far as I can tell C2 adds the appropriate information to the index.js and I made the changes to the Info.plist myself. I could not get Xcode 4.5 to run the files (dozens of red js warnings like justifun reported), but everything worked perfectly in Xcode 5.
Test ads seem to work fine although I have the same problem with the ad's placement as Zharzew said: they are aligned to the very left of the screen rather than being in the center (a bit of a pain in landscape but I think I can work around it). I've done a trawl of the Ejecta forums and a few others have asked for a solution - I only found this answer on the forum, but it's a year old and I couldn't find the mentioned file in Xcode (I've added it here in case I'm missing the obvious).
Performance was about the same as in cocoonjs, but there's no flickering splash screen! Awesome!! Now to try leaderboards....