I've never seen any contact corruption. MyPhoneExplorer does only sync certain fields, but it leaves the other fields alone. So, if you have a Business Phone 2 field in an Outlook contact, you can't sync it to your phone, but nothing is deleted.
If you modify the contact using Google (either on the PC or on the phone), you can't modify a field such as Business Phone 2, but syncing back to outlook doesn't delete that field.
My experience has been with both Windows Vista and Outlook 2007 and Windows 7 with Outlook 2010.
Perhaps I'm doing something wrong, though.
I don't use MyPhoneExplorer to sync Calendar events, I use Google's Outlook Calendar sync instead.