GearLive just found that the MobileMe update is live on Apple's site, even if it's not live on Software Update yet. Click here to grab the package, which you can install first before the actual MobileMe is live. According to .Mac's left column, the service will be taken offline between 8PM tonight PDT and 2AM tomorrow morning. If we're lucky, their maintenance will finish quickly and everyone will have MobileMe shortly after 8. If not, it'll be early Thursday. [GearLive]
You shouldn't have a problem at all getting two email accounts working. The problem is with syncing your personal calendar and contacts (through outlook, ical, or address book) when syncing with exchange. Apparently you will only be able to sync your exchange contacts and calendar, but getting gmail setup should be simple to do. As far as I know, gmail contacts and google calendars won't be able to be synced. This would have to be done through outlook or address book.
Do most corporations that use Exchange let you sync personal contacts and calendars on a corporate phone anyway?