That may change now that Todo for Mac has been announced for the Mac App Store and features cloud sync with the Todo Online service. Previously you had to use Appigo's sync client on your Mac to sync your iOS apps, or use a third-party service like Toodledo.
Todo for Mac is a compelling app even without sync, however, adding things like Task Zooming™ and Multi-Adaptive Windows™. Yep, those trademarked features sound pretty cool, but we'll have a hands-on later this week with more details. For now, know that Task Zooming allows you to change the amount of detail in a view, seeing perhaps only the todo itself, or more details, such as due dates, alert times, etc.
Multi-Adaptive Windows allows you to have more than one view available at a time, and allows you to arrange windows in a way that you can see a week's view and urgent tasks for the day all at once. Sounds great, and it comes close to being more like a project manager than a simple "to do" application based on lists and alarms.
The cloud sync side will cost you a bit more than Toodledo (which costs US$14.95 per year for a Pro account, and that's what I use), but not much more at $19.99 per year. This will allow you to sync your iPhone, iPad and Mac data effortlessly -- something Cultured Code has long promised for competitor Things but only recently released in beta. The web app version of Todo is also in beta, but the sync service appears to be ready to rock starting today. Plus, you get a free 14-day trial.
Stay tuned for our full review of Todo for Mac later this week.