Yeah, 768kbit upload is kinda lame. As they are presumably trying to compete with LLU ADSL (Be etc) I would have thought it might have been 1mbit.
Depending on the transfers involved I'd imagine 20mbit download could grab a small chunk of that 768kbit upload just for ACK packets.
Sadly I think ISPs are wary of offering home users high upload speeds due to the possibility of them running servers, together with the explosion of P2P activity in recent years.
I'd be happy to see some kind of traffic shaping on upload for certain times of traffic, provided there was a decent increase (1mbit+) and FTP was unaffected.