Agree with the last post... nearly all of the sights you'd want to see are on the other side of the river (with the exception of the Pearl of the Orient tower). But I was just there last year and thought that the subway was very easy to use. Yes, you do need to know your destination when purchasing a ticket, but:
1) the hotel staff can easily write down where you need to go, and you can just show it at the booth in the station to buy a ticket
2) the station signs are all written out in letters, so you should not have a problem knowing when to get off. (Plus, the trip across the river by subway takes about 5 min.)