When I joined up with this forum about this time of year in 2003, it was peppered with threads titled _____ ISOT'd to ______. Almost as common were variations on "Alternate Draka TL." While the former gradually faded to a slow simmer over the years and have since suffered from terminology shift, the latter actually picked up speed after the move to the new forum. Incredibly, alt-Drakas only really trailed off almost 20 years after the original book's publication. More recently, Peshawar Lancers, and (to a lesser degree) Conquistador and the Lords of Creation series have recieved the same treatment. Strangely, the only major Stirling work seemingly under-represented is his most successful - the Dies the Fire universe.
In alternate history communities in general, they are a point of reference. As board trends go, these are among the strongest. We had members - including a still-infamous banned one, who wrote Draka timelines as their primary AH activity on the site. One of our most celebrated and exhaustive works - Decades of Darkness - is partially a response to Stirling's work. Ian's Drakan timeline was itself a classic - referenced on disparate sites. To this day one can find fiction being written in universes that are alternate versions of those in S. M. Stirling's books, or even alternate versions of alternate versions.
Essentially, while Turtledove remains "the old man of AH," it's clear that Stirling has played as large a role - if not a larger one - in the history and culture of the genre's enthusiasts.
So, perhaps inevitably, I find myself contemplating alternate history and alternatehistory.com as they could have been. How would we have spent our time without the books we know, or with other ones? What else might the background history of Conquistador have been? Would airships still be considered a "staple" of AH without Stirling's works? Good heavens - how would we have reacted if he had given us a "plausible Draka timeline" (like DoD) with his books?