I've been a fan of Omni for many years, and I applaud their efforts to build their own sync service to ensure their bundle-type files get synced properly. That's dedication.

Unfortunately, OP doesn't play well with Dropbox. You can sync as many folders as you want, but those folders can't live in Dropbox, as the two sync services would probably conflict with each other. That's a deal-breaker for me, as I've recently moved all of my stuff into Dropbox, and it works so well that there's no chance I'd ever go back now.

I set up an OP account the other day, as it's the only way to sync files with the iPad version of OmniOutliner, but after playing with it for a few minutes it was clear pretty quickly that this isn't a viable solution. I'm just not willing to move all my OO documents to some special folder, away from the projects they're a part of, just so I can access them on the iPad.

At least for my purposes, this is a swing-and-a-miss. I'm sure some people will love it, and I am duly impressed with the way they've opened it up so you can run your own server and remain independent (nobody is actually going to do that, but I certainly admire the principle of it).

Given how late Omni is to the cloud sync party, you'd think they'd have come up with something amazing that works well for everyone, but alas, they went off and re-invented the wheel, and the one they came up with doesn't fit on most cars. Not the right move, IMO.