Gwen really wants to be upright these days. If she is in somebody's lap (and not busy eating), she wants to sit up or even stand up. She fusses when she's laid on her blanket or playmat, because she is sick of that view. She wants to be like the Big People, dammit!
She is more into her activity chair for this reason, though even that doesn't hold her attention forever (she wants us interacting with her most of the time, not sitting at the table eating dinner, how BORING).
The problem is, of course, that the more she sits in her activity chair (and her Bumbo, which I just bought today secondhand for $20, woot), the less opportunity she has to develop the muscles to sit up on her own. I'm *so* understanding the RIE-inspired philosophy that babies shouldn't use equipment that puts them in positions they can't maintain themselves!!