Dropbox is our favourite way to keep files synced across multiple machines, bar none, but its apps sadly don't do text editing. The universal app Elements fills that role, letting you cleanly edit text and quietly keep it in sync.
There have been a few Dropbox-enabled text editors for the iPad, but none quite reflected the simplicity and polish of the Dropbox syncing itself, something that happens with blissful reliability and speed. Elements in the best yet.
It's is a fairly barebones text editor, focusing on one document at a time, but it has some features that make it a joy. First and foremost is the Dropbox syncing itself, which happens when you open the app or every 30 seconds otherwise. If you're offline, it'll sync the next time you've got a Wi-Fi connection. The app creates an "Elements" folder in your Dropbox, which means that you'll need to be sure to save text files you want to edit on the go into that folder specifically, but otherwise the syncing worked flawlessly (and supports access to file versions via the Dropbox website, if you accidentally save over your opus).
Elements also has support for TextExpander, an app that lets you create shortcuts for phrases you type with annoying regularity. You can pretty up your text with some fonts, sizes, colours and a file info icon shows word, line and character count and the date on which the file was last modified. Another unique feature is Scratchpad - a little window, accessed by tapping an icon, for jotting down quick ideas that don't quite fit into a bigger document.
The iPhone app strips all the extra stuff away and leaves you with just plain old text editing.
The universal app is $6, a tick more expensive than some of the alternatives, but for those who already rely on Dropbox to keep files accessible on the go and have always wished they could edit those files on the go, it works beautifully. [Elements (iTunes)]