So here is a handy tip if you type a lot on the iPhone and are frustrated by all the tapping it takes to get to and from the "punctuation / number" screen. (that is the one you access by clicking the .?123 button on the lower left.
Try this next time... when you tap the ".?123" key, keep your finger down (don't release) and then just drag out to the punctuation or number key you want... NOW release. That item is typed and the keyboard automatically returns to the alphabet where you most likely want to be. Of course, this all assumes that there is actually someone left on the planet who still types in complete sentences and uses punctuation ;-)
ps... in case you don't know, here is an extra punctuation shortcut for you... when you get to the end of a sentence, just quickly tap the space bar twice. That will put a period at the end of the sentence, give you a space after, and set the next thing you type to be a capital letter.