My limited experiment was this...
For the group "a.b.mom"
Erased the data directory on the spool_v6 using "Post Storage" -> "Delete Stored Posts"
Set to download 1 day of headers to empty group
Competitor A reports 7.5 million new headers
Competitor B reports 12 million new headers
NewsDemon reports 223 thousand new headers
My conclusion: No. Even after a month, NewsDemon is not usable as a primary provider.
Too bad too. They have been reliable with good customer service (for me anyways) for years.