I use OmniOutliner 3 very regularly for school notes and other lists. Generally, the app is a good one.

I have found some bugs with the column titles. They are ones that I experience quite often and worth mentioning.

1. Not being able to change the format of the column title to align->centre.
2. Column title disappearing after changing the text in that cell and then clicking on to the rest of the document.

OmniOutliner3 was notified by other users including me of these annoying bugs and said they were working on the problems.
However, the end result since I noticed these problems about half a year ago seems to be a continuation of these problems. OmniGroup doesn't give enough bug fixes.

That being said, the application is easy to use, looks good, and generally works the way you want it to work.

If not for the lack of bug fixes I would give it a 5. All things considered it gets a 4.