The Power Pack will set you back just under $3, but that's a small fee for what you get in return. The biggest feature, for my use of Dropbox at least, is push alerts. You not only will receive alerts if you're using the app that a file or folder has changed, but you'll also receive push alerts on your iPhone when files are added or deleted from your account.
This is a critical feature for someone who is routinely waiting for files to be added to Dropbox. I do a weekly video series for another publication, and before Boxie I was constantly having to open Dropbox on my iPhone to check whether the audio files had been added to a shared folder. Now with Boxie, I receive an alert in near real-time (I've seen the alerts show up instantly, or take as long as 10 minutes to show up on my iPhone) and can begin working on the files as soon as I see the alert. Why the official Dropbox app requests permission to send you alerts but then fails to do so is beyond me.
Also unlocked in the Power Pack is the ability to view and restore past revisions of files along with deleted files. This comes in handy should you accidentally delete something, or need to recover an older version of a document.
In addition to the normal sharing methods, the Power Pack also offers a direct-sharing option for fellow Boxie users.
I've already more or less stated this, but it's worth clearly stating: Boxie is the best Dropbox app available for iPhone. There are only two drawbacks I see with the app right now.
The first is the lack of an iPad version. I do most of my mobile Dropbox management on my iPad. Being forced to work on a smaller screen isn't a deal-breaker as the most valuable part of Boxie for myself is the push notifications, but it's definitely an app that would be great on the iPad.
The lack of automatic uploads for photos and videos, akin to Dropbox's own Camera Upload feature, is the other drawback.
With Boxie on my iPhone, aside from leaving the official Dropbox app installed only to handle authorizing third-party apps that integrate Dropbox (such as iA Writer and 1Password), I see no reason to even launch the Dropbox app anymore. I only wish I could have it on iPad.