Here is my situation. Most all I do and want sync'd to the iPhone is on my Macbook. This includes my personal contacts, music, video, podcasts, photos and bookmarks. What is on my work Windows XP computer is my schedule in Outlook.
I have tried multiple solutions. First, I connected to the work network via Entourage on my Macbook and sync'd the calendar via Entourage. Entourage had issues with any Outlook event that was and all day event. It put part of the event the day before and created duplicates. So that did not work.
Next, I tried the new Outlook to Google Calendar sync to get my schedule in Google Calendar and then subscribe to the calendar in iCal. However I could never get the Outlook to Google Calendar Sync to work. I may be due to the corporate firewall.
So I decided to try syncing just the Calendar on the Windows PC. I plugged in the iPhone, made sure no syncing at all would take place. Put a check mark only under syncing Calendar with Outlook and pressed sync. It gave me a notice that the iPhone was paired with another computer and did I want to merge or overwrite the data. I clicked on overwrite and prayed. It worked. I have my Outlook calendar on the iPhone and no other data was messed with.
I then connected the iPhone with my Macbook. I made sure everything was selected correctly EXCEPT the calendar. I also got the merge or overwrite question regarding the contacts and bookmarks. I believe this is due to the calendar, bookmarks and contacts all being on the same tab in iTunes.
Therefore, whenever I move from the Macbook to the Windows PC, it will ask to merge or overwrite. Not the most elegant solution, but it seems to work so far.