I've used some poplar, in particular I sawmilled approx 20 poplar timbers for a building that did not get built. These timbers were 10x12x25. The timbers got some joinery cut, then sat indoors for a year and now they are back at my yard for sale. I would say that where the grain is good, the timber is good, and checking, twist and bowing all seem to be within reasonable limits. That being said I would definitely put poplar in the category with spruce, red pine, and other less stable timbers and suggest to anyone who uses it that they saw 20% extra so that the worst timbers can be culled and resawn into smaller pieces.