Thanks! That works!
The basic element hiding rules listed here - https://adblockplus.org/filters#elemhide_basic seem to work. With the exception of tags. If a tag such as div is specified then the rule stops working.
I have converted my custom filters to remove all tags.
There is virtually no documentation about this anywhere. Not even in the release notes! It would be great if a manual for the general syntax is specified online somewhere for advanced users. Users who are unaware might just port their ABP custom filters, hoping that they would work. An online conversion facility to transform filters in other syntax to Opera syntax would also be useful.