My guess is that the phrase "church of Oprah" is synonymous with the "cult of Oprah" - the personality cult that surrounds this truly extraordinary woman.
Now, I am sure some will find cause for criticism in the level of devotion Oprah's fans show her: the "fanatacism" of some of her admirers may seem a just cause of concern. However I cannot say I find it particularly alarming. I think that for the most part the praises showered on Oprah are well deserved.
I think she is a remarkable exemplar of empathy, and a fundamentally principled and humane person.
She's not perfect: her feminist instincts are suspect. And she once made some stereo-typical comment about the Caribbean, projecting it as a dumping ground for second-hand clothes, inferior fashion or some such thing (I'm from Barbados).
However, I think that if persons seeking a model of spirituality are adopting Oprah that is no cause for alarm. Frankly, they could do a lot worst.
As for the Eckhart Tolle "New Earth" question: I don'trecall hearing of him or his book before today, so I feel hardly qualified to offer a well informed opinion.
I can only say that based on what I have read on wikipedia (http://en.wikipedia.org/wiki/Eckhart_Tolle#Teachin... he seems to be both praised and censured by christians. I'm afraid this is not very helpful, but I would want to read "New Earth" myself before I say any more.