The shuttle is actually something I fly a reasonable amount so I'll offer an opinion...

The aircraft change will be basically irrelevant to most pax. This is because for many, many of them the purchase decision is made for them by a corporate travel desk/manager that buys either bulk tix or negotiates a special rate. (I just stick my T&E CC in the kiosk and it spits out a discount ticket). Since the decision makers don't tend to fly the shuttle and are (I would guess) evaluated on financial performance- I would guess their primary concern is price and convenience, which I think US has nailed on these routes.

So I think the switch makes good sense for US. Also the flight is so short typically that most pax probably won't even notice the equip change!

-H