Honestly SIM migration is terrible. It worked on dumbphones for me in the time of the Motorola V600 and stuff, but when I went to SE phones they could only parse each other's formatting. My Symbian based N82 had trouble splitting numbers into categories from my SE phone.
Android didn't do a good job either, so I'm not sure if iOS will either. Outlook is usually a good bet.
OP: Google sync for the iPhone is excellent. The question is how you want to get your contacts onto Google. You might've tried OVI, but I know it gives you a CSV.
If you upload the CSV via Google Contacts (web) from your PC, you might be better off than getting your phone to take a CSV file. Or if you sync to Outlook and use the CSV export there. I just feel like using Outlook might be better than relying on a half complete mobile sync system, especially from Symbian's end. Perhaps thats changed since Feb 2010, but who knows....