You may be disappointed in some areas of the gamepla in Battlefield 1943. Certain things are missing... aside from the numerous amounts of maps. I just thought I would warn you.
When in a ship or plane as a passenger in 1942, you had to wait until the driver lowered the door in order to run off into the fight. However in Battlefield 1943, you simply appear behind the ship magically, and I have heard several people complain saying that it takes them out of their element in a way 1942 never used to disturb.
Also there are less classes, and no customising for your personal arsonel in Battlefield 1943. There are four weapons, three of which have different japanese/american models; however these weapons act the same. They are the sniper rifle, the SMG (Thompson for US, Type 100 for Japanese), the rifle (Garand for US), and the pistol (which only snipers carry).
Oh, and theres no ammo in Battlefield 1943, its unliminted! So, take that anyway you wish, but I consider it a con. (Bazooka rounds just need to be "reloaded" during which time you cannot use your rockets. However, if you evade smartly you somehow are carrying around hundreds of RPGs.)
Once you can accept the fact that Battlefield 1943 is a watered down sequel (or "Bad Company-ized") you can start to enjoy it more.