My first wood score I ever posted here years ago was a big pickup load of tulip poplar. I wasn't a fan of it, but it was free. I'll grab poplar if it's free, but I'll never buy it. It dries fast, but it is horrendously perishable, keep it WELL off the ground, or you will see fungal blooms on the bark that put a Jackson Pollock painting to shame. The big downer for me regarding poplar of any variety, is the acrid, bitter smell of the smoke, especially if the bark is attached (and those damn barbs underneath it, they're not sharp, but will still draw blood). In SW Idaho we usually burn pine, fir, juniper, and tamarack, so it always smells good. But we got this absolute fiend in our neighborhood who is reviled and hated, who burns nothing but poplar (tolerable), cottonwood (nausea), wet elm (headache and nausea), and russian olive (just kill me) in an old airtight. Nobody around here has ever heard of burning black locust (biblical plague, what? Gross!), and it is everywhere, so sometimes I load up on that.
So, if you have a good cat or clean burn stove, poplar is kosher, as long as you are not putting it in an airtight, then people will not like you. But free is free, I doubt I'd pass on it. I never used to be a wood snob, but I'm starting to become just that. Because of that neighbor.