I've scoured the web a bit and it looks like RIM has not really released an official 4.5 for the 8830 yet regardless of what the email said. I'd imagine it's only days away before the install file starts showing up for real.
bcreekski: most likely not. I've heard that the storm will be getting OTA upgrades, but I've never heard of OTA upgrades for the 8830. I'd be more comfortable doing it through desktop manager anyways...