Originally Posted by Percept
Can I (with reasonable effort) set up my own SyncML server, to avoid trusting external services with my PIM data?
I think you can -- I started to research it, but it seems 99% of the ones available (free and commercial) are java based; I have no interest in running a Java server engine on my hardware. Purely a personal decision on my part, I won't go into it.
I think the more direct answer to your question would be... how much do you want to pay for a commercial working system that you just install and it works versus how much time do you want to spend working with an open source system that will require more effort.
SyncML is a spec that runs on top of the standard protocols, so really it's about finding the middleware 'meat' to do the job.