make it possible to print out a checklist
it would be super-cool to have the ability to print out a checklist of missing issues in a series or run for taking to the comic shop. that way you have a handy list of what you don't have.
although i guess the planned mobile app would defeat the purpose of this for anyone with a smartphone.
You can print out a want list.
You can also print out a Completion report: http://comicbookrealm.com/report/completion