Hi fellow refugee!
Omni have their own sync server in beta which is free, details on:
https://www.omnigroup.com/sync/
I have used both mobileme sync and the omni sync and I think the omni sync is faster and more stable, but others may differ.
Some people I believe also use Swiss disk, but I don't have any knowledge of that. I'm very happy using the omni sync server and haven't had any problems.