My reply is as above, I fly Bristol/Newark and then onto Tampa three times a year and choose my seat at the same time as I book and have never had it changed when I get to check-in.

Don't have an answer about paying for extra leg-room, for me it is just about OK for the length of the trip but then I ALWAYS choose an aisle seat which gives you a little bit of leeway but with a one-aisle plane there always seems to be some sort of trolley up and down the aisle.

No complaints about Continental, it saves a great deal of time and hassle to be able to use a local airport.