I checked out The Leaf one evening last week. I was impressed, the building itself is quite something.
I have to admit that plants aren't really my jam, an hour in the biomes was enough for me. Although if I went there on a day off and brought some books to read, I could probably sit there for hours just enjoying the vibe. To me, the general environment in the building is more interesting and appealing than the individual plants themselves. There is even a cafe in the lobby, and you can bring your coffee inside. I spotted exactly one butterfly during my visit, but I suppose with a name like "Butterfly Garden" they aren't promising any more than that
I had dinner at Gather Restaurant after my visit and I really enjoyed that. It's a lovely dining room and the food is great with a nice selection of small plates and mains.
The only mistake I made was not bundling up... after spending the evening in a somewhat warm and moist environment, it was jarring to step outside to walk back to the parking lot. It was probably only about -12 but it felt like -30. Next time I go I will wear full parka, toque and mitts even if it's not that cold out, just to reduce the shock of stepping outside after the visit