Seems to work well. I've only come across one major issue:
We have a lot of bundles and use the Bundles app that sets the inventory of the bundle based on the inventory totals of the individual products. Syncio inventory sync seems to be triggered by either a Paid Order, or manual inventory edit... but if another app like Bundles adjusts the inventory of an individual product (because a bundle was sold), Syncio's sync is not triggered and does not sync the inventory. If an individual product of that bundle is sold, then sync is triggered and inventory levels on the source store catch up. This will become problematic if you have a lot of bundled products like we do... not sure of a good way to do bundles yet with this app and we don't really want to have to manually assign x number of items to multiple bundles in our source store.
Thanks so much for your feedback. We're looking into compatibility with the Bundles app and other options. We're getting more requests to offer bundles and we'll look to make this work soon!