Is there a good shopping list app out there that also syncs with an OS X desktop client? Or, should I just be using things like YouNote / Evernote / To-Do Lists?
Ours syncs up with the web so you can manage your list there and on the phone. A major advantage of this over a traditional desktop client is that you don't have to be near a computer to sync your list up with everyone else in your group and with the web list. You can check it out at the link in my sig.
If you don't want to type at all you should try a visual grocery list like NeedFood.
+1 for Our Groceries.I really like OurGroceries. It's available across platforms and everything is synced to a master account. All of your lists are accessible and editable from any of your devices or computers. In addition to iOS, it also works on android and blackberry.
I've had my wife updating the list while I was in the store and had no problems picking up the added items as lists are updated very quickly on devices sharing a list.Works great if my wife is headed to the store and we forgot something. I can just add it to the list and it shows up in her phone.