There is a clip on the back of the trunk for clipping on a Topeak safety light so that the bike is visible in inclement weather or after dark. (I always forgot to turn off the light when I was done riding, and could be seen walking through the hallways at work with a still flashing bicycle pack. )
It comes with a rain cover so if your sunny April morning gets wet on your ride home, you can keep that extra change of clothes you brought along dry. And, when you get to your destination, you can easily unclip the bag to take your belongings with you.
Of course, Topeak thought of that, too. It comes with a carrying handle so you are not wrestling with it.
And, if you get too addicted to commuting, you may find that you want to upgrade to the one of Topeak's real rack installations. However, for someone who isn't hard-core about commuting, but wants to have ample storage space for those trips where they do plan to commute or even just go on a long Sunday bike ride, the Dynapack DX is a hard one to beat.
So, if you are looking for a bicycle trunk that is heft without being overpowering, the Topeak Dynapack just might be the one to check out.