As I understand it, there isn't a single species of hybrid poplar, but a group of them that have been bred for different climates and purposes. The kind grown out here for pulp really do bulk up fast, though. I've heard claims that a home could be heated with a single acre of hybrid poplars on a permanent rotation, with modest harvest sizes achieved by 5 years, but the strategy sounded marginal at best. 2-3 acres and starting serious harvesting (other than thinning) in 10 years could probably do it easily.
However, I'd rather have a mix of trees that not only provides firewood, but a nice place to walk through and watch for wildlife. Besides, I think poplar prefers the wetter lowland areas, and other trees will do better on the higher spots on your property.
You'll probably get more total BTU per acre than oak, but have to process a much higher volume of wood to get it because of the low density of poplar.
So maybe you could plant an acre or two in hybrid poplars to get your firewood off to a faster start, but the rest in a mix of the sort that was there before?
As far as weed-like nature - at 10-20 years old, they should be producing only relatively small seed crops. I also don't think their seeds, which are small and as a result don't provide much nutrients to the sprout, compete well against other plants, even grasses.