I've been to DLUX a couple times in the last couple years on another's request. I'm generally not initially thrilled with the idea of burgers if I'm going downtown, however I haven't been disappointed with DLUX. I would prefer to reserve the downtown burger for 1or 2am (Plaza Burger).
There are multiple burger-alternative-burgers offered. The falafel could use some crunch or other diversified texture aside from squish (multiple veggies, sauces, falafel making bread soggy too), though the flavor is there (mmm tzatziki). Cheese curds look great; I hope to try these little bundles of cheese-joy next time. DLUX offers fun, innovative milkshakes but I can't vouch for flavor as I haven't experienced these myself (need time as well).
Burgers and drinks are priced fairly, particularly for just of the Square. Although not included, sides are inexpensive and given in large portions and multiple varieties. Staff has been okay. At one time, DLUX offered trivia but trivia in Madison is always changing so definitely check that out first.