At the outset, I must say that I am a regular user of OmniFocus on my iphone and mac. Its a very well designed product and I use it many times a day every day and cannot imagine how I will manage my tasks without it. I have tried Things and a few others and, I think, for my current needs, Omnifocus is the best fit. However, I think the sync choices in the application are unnecessarily complex and the concept of keeping things simple for users was lost somewhere. Omnifocus currently offers 4 different ways to sync data from iphone to mac:

• MobileMe (easy to set up. available everywhere. but not everybody has it.)
• Bonjour over your wireless network (harder to set up. does not work everywhere. most people have it)
• Disk (most esoteric. does not work for mac to iphone sync but is listed right there)
• WebDAV (hardest to setup. can be made to work everywhere. most people dont even know what it is)

As you can see - there are no good choices. There is nothing here that is easy to setup, works everywhere and everybody has it. I submit that when designing a product a product manager should focus on easy to setup above everything else. If its not easy to setup, it should be made easy to setup or its not a viable option. Period. In this particular case, Omnifocus should have had really one choice and one backup choice:

• company run webdav server for syncing
• a command line based  option to change the URL of the webdav server

A server run by omnifocus can be made exceedingly simple to set up, will be available everywhere, can be free (given the price of the product), available to all licensed users and should be the default, automatic choice. Its actual technical implementation could be as a webdav interface (which the product currently supports). The only challenge with it would have been that a minority of people will not be comfortable putting their data in a 3rd company hands. For that minority privacy-focused group, there should be a way to change the "URL" of the webdav server to a private server (if they want). This would have been the best compromise to provide ease of use of the users along with giving the control to modify if they want. And control is second only to ease of use in terms of what you as  a successful product manager need to give to your users.