I have seen a few setups around the traps, a nice half way point is a book for attendance and collect fees using paypal (its easy to setup). Going to dojo management software means a computer, possibly internet connection, maintaing the computer, backup strategies and probably you still need someone to drive it turn it on/off before and after class. Its all a question of scale I think if the dojo is full time with lots of people coming through the door its probably helpful, but i suspect for the vast majority of dojo its a cool idea but maybe a time sink that distracts from training
You should look into martialmanagement.com, it avoids most of these problems by not requiring anything at the dojo (though you could have a computer there if you wanted). Once your students are entered in it's just a matter of checking off who was in class. What you choose to enter for each day is up to you. Students can log in on their own time if they want to look at their records, see what content you may have added, read messages, etc.