Alright, I think that's it - was looking at this on a machine with an older eclipse install over the weekend, and wasn't able to discover the 1.5 / 1.6 change regarding interfaces. It was definitely not my intention to restrict the usage to 1.5 - to paraphrase devops borat, sometimes it is IDE that tells you syntax, not other way around. 

I do have one more question on this point - are the open/closed parentheses after Override doing anything? Those SO threads didn't seem to make any mention of it