I really want to like this app. In some ways, it's the perfect Todo manager for me - simple yet with enough tagging depth, easily accessible via the menubar shortcut, and with the promise of sync to my other Macs and iPhone.
Unfortunately, the (paid) iPhone app doesn't sync for me, and I've yet to read a single person having success with the Mac-iPhone sync. Since the developer uses a bit of sleight-of-hand in claiming sync between Macs (it requires syncing one mac to the iPhone app, then back to another mac), the mac-to-mac sync also doesn't work. Contacting the developer for support on this feature was no help at all.
So, if you're interested in only using this on a single Mac and need a simple, quickly-accessed todo list manager, it's hard to beat this app. But if you're looking to sync your todo lists between multiple devices (be they Mac, iPhone or iPad), this is not the app for you. Should the developer add sync via iCal/MobileMe and fix the iPhone sync issues (not to mention creating an iPad version), then it might be viable.