As a most-of-the-time vegetarian who occasionally falls off the wagon, I find that the reality of eating burgers at Nix generally doesn't live up to my anticipation.
I've eaten here a few times, and the experience is a little inconsistent. I order the same thing every time - the mushroom Swiss burger, medium rare. It sometimes comes out well-done, sometimes medium, and sometimes as I've ordered it.
Overall, cooking issues aside, though, these burgers are perfectly fine, but that's all.
Re: the sides, I've tried the regular fries, the sweet potato fries (boy will I be glad when this fad is over), the onion rings and the tater tots. I think the tots are the best. The batter on the onion rings has a bitter taste (beer batter maybe, but I didn't like it). Second place goes to the regular fries.
If you're just in the mood for a basic burger, this place will do the trick. If you're more of a connoisseur, you may be disappointed.