Well, the reason is quite simple; to understand this, one needs to throw quite a bit of analysis time at it, first in QA to test all scenarios and understand how they interact, then in engineering to look at it from a tracing and debugging perspective. All-in-all, the is probably anywhere between 2 and 5 man days of work, with associated cost; and you can also imagine that with a product our size and complexity, there is no lack of things to do, so surely it is competing with other things.
Looking at the Bugzilla tracking entry, btw., I wouldn't see any "lack" of priority; there's been one request of a commercial customer so far for this through support (which raises priority) and it is marked up with it and currently it is sitting there in a queue waiting for a developer to look at, and we're planning to do so for Scalix 11.5, which is our next public release. It's too big to fit into a patch release (there will be 11.4.2 sometime soon), and so far no commercial customer has asked to escalate the issue, so it's pretty much as high as it would get on the priority ladder because of this. It isn't a firedrill either, but I think given the impact and percentage of users affected, that's reasonable.
On the lighthearted side, why would you punish yourself using Windows and Outlook if you enjoy the iPhone's user experience otherwise.... get a Mac!
iPhone Mac syncronisation via Apple iCal calendar and Scalix CalDAV works just fine.....
So ... with all respect, if you were me and all things considered, what would you do differently?
Tx,
Florian.