Topify's older notifications have simplified subject lines.
The new Topify updates contain follower statistics.
Topify, who seemed pleased that Twitter is starting to follow their functionality, stealthily added a tweak to their own notifications today, changing the subject line to show not just the user's name, but also their Twitter handle and followers/following counts. For those people who might be getting a ton of notifications, or who don't want to click through each e-mail to get the pertinent data, this might be a time saver. Alternatively, it could be a simple update for update's sake. Either way, it still keeps Topify ahead of Twitter's native offering.
Also keeping Topify ahead of Twitter's standard (though improved) e-mails is that you can perform actions directly from the message. You can hit reply to automatically follow back, or on direct message alerts, you can hit reply to send the user a DM yourself. You can even forward the message to email@example.com if you just want the user to disappear. In contrast, Twitter instead only offers the ability to click through to a profile.
The ecosystem being built around Twitter is an interesting one, and each little tweak helps.