Yep... I tend to do a lot of the 'inbetweening' work myself. I generally work pose to pose, so I guess it makes sense - and I try to get a lot of the breakdowns done before I convert it all to splines (I used to do a linear pass too al a Keith Lango, but didn't see much point to that). Sometimes I'll kinda go with a 'mix' method, doing the main key poses and then break straight into splines... then do a lot of work in the graph editor.
But yeah... there are times when I will key an object on every frame (so it doesn't matter what the graph looks like between the keys). It's not often I'll do it - I guess it's not a wholly sensible thing to do - but there are times when it's almost necessary to get, say, a hand to do exactly what want it to do (especially if I get gimbal locks etc). I have to be at a point near the end of the anim, when I'm pretty happy, before I do this. Actually I pretty much did this today - animating a monster lashing out at something, but having a real problem getting the arm to look right but maintain a good sense of weight. I had to really break down the motion, the way the elbow crossed the wrist etc, to get the shot working.
One bonus is that it really does make you step back from the technical side of things, (ie worrying about the smoothness of splines or how a tweak to the shoulder will effect the elbow and the wrist etc) and look at it a little more artistically, really analyse the forms and poses... you really start to feel like you are animating!