I need a good "to do" list organization app. The Things app seems like it would be perfect for what I need, but they want $19.99! What a joke. I just can't bring myself to pay this much for a to-do list app no matter how pretty or robust it is. Can anybody recommend a good alternative? I'd like to be able to check off items as I complete them and I'd like it to sync to my Mac. It would be nice if it had a nice layout and good system for organizing lists. I've found a couple on the App Store, but most reviews say they have major shortcomings or they crash.