Hello all, still reading through the thread but thought I'd jump in anyhow. At our place which we focus on traditional the Sazerac is brandy base as it was meant to be, however we do offer it with Whisky (Gibson's 12yr) or Bourbon. My son has adopted this drink as his signature and has created a couple of devotees. He has developed a wonderful technique of rolling a round ice ball in an old fashioned glass to distribute the absinthe (yes we get the good stuff in Canada) and consistently hits the perfect amount that no dumping is required. This is the last thing he does before pouring the stirred brandy/rich simple syrup/bitters over the ball as well and garnish with a twist of lemon peel. The ice ball looks sharp and gives a unique and distinctive look to the drink and allows the glass to be appropriately full with a 2oz pour (not quite as traditional but marketing has to factor sometimes and this is once where departure from the line of tradition works well)
Myself I far prefer the sazerac with brandy as intended than with either whisky or bourbon. If in the mood for either of those I will go to the traditional Old Fashioned (my personal favourite and signature cocktail).