The SMASH burger is indeed amazing!
My friends and I went there for dinner on a weekend. We made reservation at 6, which was not super busy when we arrived. It started to get more packed after 7, but I think if you are coming with a group of 4 or less, it shouldn't be too hard to grab a table without reservation.
The SMASH burger comes with 2 juicy and beefy patties and some crispy onion rings (inside the burger) and a side (choice of soup, salad, or fries). I highly recommend getting the fries as they are slightly thick-cut and freshly deep fried. The portion for fries is also larger than salad or soup. My friend and I both got the SMASH burger and shared the sides - one order of salad and one order of fries, but we still couldn't finish the fries. The fries are more than enough to keep you satisfied and full.
The service was alright. One of the servers seemed to be in a hurry and always wanted to take our dishes away. Other than that, the overall experience was great.