@BobRyan @Albion @Ignatius the Kiwi @imge @Danthemailman @Freth
I was a member of the Seventh-day Adventist church most of my life, and a pastor in the Adventist church for ten years. I left due to an inability to reconcile some of the doctrine (the investigative judgment teaching initially).
There is a lot I love about the Adventist church. The average member tends to be quite dedicated. And I think many are walking in Christ. They do have a number of teachings considered heterodox, as has been already discussed.
The majority of members do hold to a view that is mostly in line with Trinitarian thought. Though there are still a minority who are non-Trinitarian, and as Bob mentioned they are non-creedal. His statement that if a creed happens to agree that is fine, but they don't go by it is quite accurate as describing most in the church.
Most Adventists do see a falling away from true doctrine on a number of points rather early on. So even the fathers of the early centuries following Christ they would usually see as wrong on hell, death, etc. In theological training we did read writings of the church fathers. However, there was considerable emphasis on the differences. Many Adventists do no reading regarding the early church.
Bob was correct that they did not draw doctrines from Ellen White's writings, with the possible exception of some of the health message initially being pointed out in vision.
However, Ellen White's visions were used to confirm understandings of Scripture that some had already come to. They do not consider Ellen White part of the Scriptures. However, in practice, if Ellen White comments on a particular Bible text few Adventists will argue against the interpretation given, because they consider her inspired. And she commented on a great many Scriptures.
Regarding ecumenical endeavors, a lot of Adventists engage in ministerial alliances, joint relief efforts, religious liberty endeavors (which they are quite strong on given their experiences in Sabbath workplace discrimination), etc.
And they generally consider that Christians following God to the best of their understanding are still saved. That includes historical figures, reformers, etc. However, that does not mean they have a particularly positive view of other churches.
Most Adventists and Adventist apologists indicate that they see themselves as an extension of the Protestant reformation, and that they feel the Seventh-day Adventist distinctive doctrines are a further calling out of error from what was brought about by Luther, etc. However, by most outside viewers they would be considered restorationist.
As to how they treat those who depart from Adventist understanding, I think Bob knows a bit more than he is letting on. Yes, it varies. However, I have known a lot of former Adventists, and many have had family and friends consider them a heretic and lost.
On the other hand, I was treated quite fairly by the leadership when I departed. And I think they have developed better habits on this over time, as a number of clergy have departed over theological teachings. This is especially true following Desmond Ford raising issues on the Adventist investigative judgment and sanctuary teaching. In Australia and New Zealand this was more pronounced than in the USA.
Overall, I still love a lot about the Adventist church, and didn't want to leave. However, I felt convicted that it would not be right to stay and minister there if I did not agree with their fundamental doctrines. Their doctrinal statement is quite thorough, expounding on a number of points.
The teaching that most relates to this is the view that they consider the movement to be the remnant church of God, and that God calls others to join that movement. So while they may see others as sincere Christians, they see other denominations as essentially babylon, and believers to be called out of them.
