Echofon for Twitter
The popular Echofon for Twitter app has an excellent lock screen widget that fits right in with the Android 4.x design aesthetic. The Echofon widget features tabs for your timeline, @-messages and direct messages.
Unlike Falcon, Echofon does display direct messages right on the lock screen -- which could be a plus or a minus, depending on your perspective. The app requires you to unlock the device before composing a new tweet.
Echofon for Twitter is available for free; an ad-free "pro" version is available for $4.99 (though even in the free version, ads don't actually appear in the widget).