After spending nearly six month out of the anchor's chair to receive a bone marrow transplant, Good Morning America host Robin Roberts is back on the air.

Wednesday's "Very Special Edition" of Good Morning America began as a grinning Roberts said, "Hi, it's Robin, and I have been waiting 174 days to say this: 'Good morning, America!'" The morning's highlights included taped messages from Oprah Winfrey, Hillary Clinton, and the Obamas, who told Roberts that the whole First Family had been "thinking about you and praying for you and rooting for you every step of the way."

The morning also featured an interview with Roberts' physicians, Dr. Sergio Giralt and Dr. Gail Roboz, who cautioned that today's episode was a "dress rehearsal," and that they're still waiting to see how she feels tomorrow before she can return to the show on a more permanent basis. "I don't care who the interview is with: If you're not well enough to go, you're not going," said Dr. Roboz, prompting Roberts to reply, "That's what I want to hear."

Roberts' medical ordeal began when she reported exhaustion while covering the Academy Awards in February 2012. After a series of tests, doctors diagnosed Roberts with myelodysplastic syndromes (or M.D.S.), a rare blood disorder. Roberts announced her diagnosis on Good Morning America in June, and took a leave of absence in late August to undergo a bone marrow transplant. Last week, co-anchor George Stephanopoulos announced that Roberts plans to be on the red carpet to cover the Academy Awards this Sunday — one of the goals she set at the beginning of her treatment.

Sources: ABC News, The Hollywood Reporter, USA Today, New York Times, Huffington Post