Opera is attempting to get their browser approved for the iPhone. This means that the Opera browser might be something that users can download and choose to use as opposed to the mobile Safari addition. Despite this being a difficult task and too much effort according to Mozilla, Opera is going to try to change this. First, this is a good for those who love choice. Opera will be able to compete with Safari bring other elements and features to the browser. This means that iPhone users will most likely get better features since there is some competition.
There are already some good'ns out there though. Atomic and especially Dolphin are two which shine for me - the latter being free. Plus, if you're jailbroken, there are loads of tweaks for safari which improve it significantly.