On a chilly fall evening I went out to LaBoom with a colleague from Montreal who's never been there himself. The place is massive, 3 floors of varying music and a loud, energetic albeit very inebriated crowd.
With that said, I feel the 'popularity' of this place lies in the fact that Montreal's nightlife consistency can vary so widely. A near perfect example of this is that on this night the ambiance in this joint was very irregular, one floor had a seemingly lively rage going, while the hip hop/dancehall floor was mediocre at best.
Drinks are ok not great, so I would pregame semi heavily and stick to beer.
Staff was relatively chill except near the coat check line where the bouncers seemed more bent on flirting with drunk 18 year olds than keeping the like moving, it was only 11:30 with a half empty club, shouldn't have taken so long.
In conclusion I'd think hard about coming back here, I feel it's worth giving other places a shot especially when you're there on a weekend trip, even when doing 12 or so Montreal trips last year alone.