Mr. Smartypants who thought I wasn't watching . . . pulled himself to standing at the stairs on Wednesday! It took some practice, a few tries, and he did it! I had my cell phone in my pocket so I managed to get a (albeit slightly fuzzy) picture of him standing. He can do it at the couch now too, if you give him a "cue" (one finger under an armpit gently nudging him up). And I noticed yesterday and this morning that now when he "inchworms" across the floor, he's really picked up the pace!
I think I need to child-proof the house at a higher level because he's already eyeing the dining room table . . .