I was a straight Mac system user, so OF on mac, and iPhone was great. As I now am on a windows (groupwise) system at work, I've had to turn to my iPad OF as a solution, although definitely not the easiest.
I email tasks from my work inbox to my mail at home with Apple Mail and OF running on my iMac. The rules add each specific mail as tasks in my inbox. I've tried the 'send to OmniFocus' link, but it doesn't work that well for me, due to some configuration on our office mail server, which scrambles the link.
I tried using Nirvana, which looks great and showed some promise, but I just found I missed the power of OF and the great syncing across the platforms.
An OF web-interface, which would sync with the other platforms would be amazing. I also tried Nozbe to see if it could deliver, but I just found the interface difficult to work with. I even tried Spootnik, linking through Basecamp, but again just not that functional for me.
My final hope is either an OF for windows (which I doubt will ever happen - thankfully) or a web interface that can sync with the OF database.