The author who got a lot of people into AH. He is, however, not that well respected on the Board, as many people believe he has sold out in recent years and turns out piles of poorly edited populist dreck just to get his kids through college, rather than the fun pulpy stuff and interesting Byzantine history of before. The main problem people have with Turtledove's recent books is his habit of describing his viewpoint characters' simple character traits at least three times per book. The most commonly cited example is Sam Carsten (from the Great War books) sunburning easily.
“Turtledove's repetition” is a common running joke on the Board, cited in parodies and comedic works such as AH.com The Series, Luaky Commer, etc., etc.
However, the Board's achievement awards in AH are named the 'Turtledove Awards', in memory of HT's heyday.
Discussion on Turtledove's capabilities as a writer
Discussion on Turtledove's popularity as an AH writer
The Turtledove That We All Love - A somewhat tongue-in-cheek narrative tribute to Mr. Turtledove, by David Bar Elias.
Harry Turtledove's Official Site
Turtledove is giving a lecture at my college - An audio recording of the lecture is available here.
TV interview with Harry Turtledove