[whpalmer4]

If you convince yourself that it won't work, then yes, it won't work. Even though none of them support Dropbox directly, between OmniGraffle, OmniOutliner, OmniGraphSketcher, and OmniPlan, I get a lot of mileage out of a WiFi-only iPad, and have yet to lose a change despite frequent switching between Mac and iPad and quite a bit of offline use of the iPad. (They all use the same framework for file access/storage)

What's more important to you, having access to OmniOutliner, or not having to think? Right now, you don't get to use it at all. Surely getting to use it most of the time is an improvement, no? You do get a view showing you when you last edited a document (sorted by modification date), so figuring out which ones you might need to sync isn't so bad even if you didn't have the presence of mind to make a note of them at the time you changed them.

I think you should try it out, and if it turns out not to be workable after an honest attempt, contact Omni for your refund within 30 days of purchase. Be sure to tell them why you threw in the towel.