Switching between the alphabet keys and number/symbol keys on the keypad can be a bit annoying, especially when you want to quickly insert a number or symbol and continue typing text (alphabets).
You can avoid a few extra keystrokes if you press the ".?123" key and then without releasing drag over to the number or symbol you want.
Assume you are typing an email. You want to type "Let's meet at 3." You can type the word Let, then press and hold the key ".?123" and drag over to the single quote and release. The keypad will return back to alphabets after the single quote is inserted. You can type the rest of the message and when you're ready to insert the 3, repeat the same steps this time selecting 3 before you release.