We're exactly in the same situation, but our devices are blackberries. We too don't want to bother with any windows server at our end.
I've been testing Nofifylink with Saclix for just over 1 month now, using their "Hosted Service" instead, but so far only the Over-The-Air IMAP sync part works. The MAPI part (calendar, contacts, tasks) still lags on the integration with scalix. So for now all other users sync with the desktop via USB cable.
I saw a couple of posts on this forum mentioning Funambol, one of them even claiming integration success with scalix
viewtopic.php?t=2202&highlight=funabol
It's just that the subject has been very quite one the scalix side, and I don't want to spend the time to pursue this further on my own or add another variable to some of the remaining problems still to be solved.
We tried zimbra in-house before scalix, and at that time direct over-the-air sync didn't work. They also required Notifylink. I keep on eye on the zimbra forum as well, and they still have their own set of problems with this integration.
I'm sure scalix is not sleeping at the wheel, and they must be cooking up something already. That would be a very nice addition, provided that it has scalix support under linux and it works.
But for now I don't want to know what it is. I'd like them to focus on some more pressing matters.
Jaime