Ordered delivery from here using UberEats. I'm a fan. The burger is somewhat comparable to the one from Five Guys (in my book, a high compliment for fast food). Very similar style - some choice of fixins (less than Five Guys), option for two patties that are fresh, inclusion of gooey cheese. I think the price point is slightly higher than Five Guys (but not substantially different) - though this may be a thrid-party delivery markup (I haven't checked). Certainly not expensive.
The main differentiator between Uniburger and Five Guys is probably the option to get a milkshake from the former (Remark: Five Guys offers this as well at some locations - but, last I checked, not in the Montreal Old Port location). The Uniburger name suggests that their "Uniburger" option should be a differentiator as well - but I don't feel this is the case. Slightly difference sauce - no biggies (for my taste buds at least).