Poplar (Trembling Aspen, not Tulip Poplar - different family altogether) has about the same structural strength as the Spruce and Subalpine Fir found in S-P-F designated lumber. It's just fine for studs, though I don't think I'd use it for other structural applications such as truss webbing. In fact, since the Pine Beetle has destroyed our Pine stands here in BC, people are starting to talk about milling Poplar for light structural use since it grows extremely fast, with millable trees in under 25 years in the right conditions. It isn't rot resistant at all though, so as stated keeping it dry is important. The other uses already pointed out are the more common ones. Around here I regularly see whole logs going south to the pulp mills on the trains.
BTW, nice tabletop Chev. If you use a finish something like Varathane Diamond Hard etc. the relative softness of the wood shouldn't be a big problem. I have a few big Poplar slabs out back that I've been thinking of doing the same with.