There are those who are former XCGers and now who have embraced Evangelical Christianity who believe very strongly and passionately that tithing has been superceded by The New Covenant over the Mosaic Covenant. The late great founder of The Center of Judaic Christian Studies, Dwight Pryor had some interesting insight of tithing and Christian giving. Worth a listen no matter where you stand on the topic. Listen here.
Life After The WCG: A Spirital Pilgrimage of an Independent Believer 