After much experimentation on several visits, I finally hit on my favorite build-your-own: a single with grilled onions and blue cheese on a sesame seed bun. (Of the three cheeses I tried, the blue was the only one that had any noticeable personality.) I also enjoyed the vegetarian black bean burger, lightly grill charred and with a little back-end kick from vaguely Mexican seasonings, I'd guess cumin with a touch of chilies. Turkey burgers are also available; the turkey I tried was the juiciest of the lot but also the greasiest, even in the single size (the grilled onions may have contributed to that).
Sampling among the six preset combination "signature burgers," we were derailed by the Train Wreck, whose trademarked name is a fitting description of this compilation of meat, fats, and starches: two beef patties, that same flavorless cheddar, fried onions, fried mushrooms, a fried egg, french-fried potatoes, and mayonnaise in a soft white bun. Less would be more here; the smooshed fries were excess baggage, the egg overcooked. The Blues Burger was on a more modest scale, with just two meat patties and blue cheese, but it suffered from a large dose of incongruous Cajun spicing, and the unpleasantness was compounded by a stale honey-wheat bun. (I will say that that was the sole dated bun among many fresh ones, and that generally the buns stand up well to the meat.) But we liked the bacon BBQ burger, which came together well with crispy bacon and a fine barbecue sauce.