Well, it sounds like there's a decent possibility that you're running into a bug that causes some very inefficient sync processing (it happens on the desktop as well as the iPhone/iPod, but the greater processing power of the desktop tends to mask it). Ken posted a while back that he thinks he has a fix, but wanted to do some extensive testing internally before releasing it.
If you email the support ninjas (via Help->Send Feedback, or email to
omnifocus-iphone@omnigroup.com) or call them up during normal business hours in Seattle at 1-800-315-OMNI, they can walk you through the steps to confirm that this is the only issue.
A symmetrical connection is one where the delivered upload and download speeds are approximately equal. Most residential users download much more traffic than they upload, so the telco's infrastructure budget goes farther if they don't try to provision the links to be symmetrical (and it gives them something extra for which they can soak the customers who need it, such as a business with a need to send more data).