I haven't come accross this problem personally, but I would have thought when you connect it, it should be fine. If it doesnt work, do a forced reset and when it tells you to connect to iTunes, do so on your new iMac and it should be ok.
Can you tell me why you've switched to an iMac from a PC? I'd love to do the same, but not sure its worth it at the moment.
I only use the PC for music, photo's email and internet. The iMac seems a better solution for all of that stuff (all the software like iPhoto is pre bundles in the OS where with a PC you have to but the specific programms you want). Also, the PC takes up alot of space which obvioulsy an iMac will not.
I also switched for the reasons above plus I was sick of antivirus programs and spyware programs and updating them. The computer system is similar to the iPods and iPhone. They just work together and are intuitive. It takes about a week or two to get really comfortable but once you do you won't regret switching.
As far as going to a Mac from pc for the iphone the computer will notice you were synced to a different computer at first. You just need to sync to the mac or do the restore function if you want to start from scratch.
If I do not reset the iPhone, will the Outlook contants and calendar be synced FROM the iPhone to the MAC? (photo's and songs will be deleted from the iPhone I presume during the sync if I have not specified directories for each?).
Well, the first time you sync your iPhone to your Mac, you will be given the opportunity to sync back the PIM data (calendar, contacts, bookmarks) and either merge it with any information currently in the Mac applications (ie, iCal & Address Book), or replace anything in those applications.
If you haven't actually setup any data in iCal or Address Book on your new Mac, you can select "Replace Info" safely enough and the information from your iPhone's calendar and address book will be transferred to your Mac.
Other content such as music and videos will be removed and replaced with the corresponding content from the iTunes library on your new Mac, so you'll want to either transfer your iTunes library from your PC separately, or look to a tool that can recovery this information from your iPhone (www.findleydesigns.com has one of the few applications for this I'm aware of that is iPhone compatible, although if you also have a traditional iPod model there are numerous other software applications for this as well).
I just got my first Mac a couple of months ago and I was surprised by how wonderful it works. The way I have my music set up is on our desktop PC and I have close to 60GB in music and audiobooks. I didn't want to put all of this on my MacBook with 120GB HDD so I still sync my music through my desktop and I sync all of my contacts and calendar items with my Mac. This way I don't have to enter all of my appointments and things on my desktop. Works beautifully.