Apple did a good thing and updated the operating system for both iPad and iPhone. I'm generally leery of upgrades because sometimes they are not improvements. I did not think iOS 7 was an improvement from iOS6. Given that, after I "upgraded" my iPhone 5 to iOS 7, I did not upgrade my iPhone 4.
My story is different if you are running iOS 7. Get the update! It's a huge improvement. They changed the font color from medium gray to black. I can finally see the letters clearly. They also changed the color contrast on the keyboard, making it easier to see too. Navy blue was added to the color font for the address book, better delineating lines and numbers. Folder color was changed too...it no longer blends in with the wallpaper making it easier to see folders. On the iPhone they changed the look of the phone dial, again, making it easier to see. I'm sure other "fixes" are included, but the fixes I can see are worth the 10 minute installation time.
I'm guessing a lot of folks, me included, complained about the lack of contrast between the background and the font color. They listened and made some much needed improvements. If you have not downloaded iOS 7.1 and you are using iOS 7, make the change. I think you will be pleased with the outcome.