Dave, no I haven't carved poplar before, and have only worked on the wing so far. My scroll saw left a fairly ragged edge using a blade that would have left a very clean cut on basswood. I'll keep you posted.
Regarding poplar, for me it doesn't carve like butter but it is easy to carve. I use carving chisels and knives as opposed to woodworking chisels. On my scroll saw, I use the coarser blade that usually comes with it. This blade leaves a nasty cut on basswood but is very smooth on poplar. I had bought a finer blade to use with basswood but have not changed it yet. From the pic it looks like you are using the fine blade, maybe the coarser one will work better on the poplar. I also use a fairly high speed on poplar.