My main hesitation for trying BOG (aside from the near impossibility of getting an ADR) is that I'm a bit of a signature snob when it comes to restaurants with gourmet theming.
That being said, I love many of the non-signature dining experiences at WDW. I love many of the character breakfasts. I love 'Ohana and Kona. I love Via Napoli. And I really like 50's Prime Time. I'd like to try Biergarten, Hoop Dee Doo, Teppan Edo, Sanaa, and Boma.
But none of these restaurants are trying to be gourmet (their themes don't require it) and I don't go into these places expecting gourmet-style food. But if I go into a gourmet-themed place, then I do expect food of at least a nominal gourmet-esque quality. And I view BOG as a gourmet-themed place.
In that regard, my experience with gourmet-themed non-signatures at WDW has been one of disappointment. In order avoid disappointment, I've learned to stick with the signatures (which usually meet, and sometimes exceed, my expectations). This has conditioned me to base my frame of reference of gourmet style with signature quality. Given that frame of reference, I'm highly skeptical that I won't be disappointed with BOG.