I've harped on this in at least 5 different threads, but hell why not? I'll say it again.
Add the ability to create/save groups in your contacts so you can quickly email/text an entire group.
Make it so ad hoc group texting/emailing doesn't force me to hit the plus button and go through the list of contacts every time I want to add another person to the list of recipients, and instead just lets me check all of the people I want at once.
Those are the two glaring weaknesses I personally would like fixed.
My 4+ year old Sanyo M1 handled group texting better than my iPhone 😡🙁