"If I had asked my customers what they wanted, they would have said 'faster horses'"
-- Henry Ford (unsourced)
You don't write on books because it's permanent and possibly damaging; Post-Its caught on as a way to work around that.
The (e-ink) Kindle solves the speed+versatility vs power+weight compromise by specializing in a task that requires little of the first two. Arguably, virtual Post-Its don't require a change to that compromise; a better, more interoperable implementation doesn't cost extra.
PC integration? Sure, just sync in a simple, flexible way (i.e., not iTunes) to a PC/Mac app or to your account through the WiFi link you already have on board.
Speech recognition? Now that's expensive, even more if done offline. At that point you should consider a tablet.