The download is around 27MB, and that's if all your firmware is up to date, so Ovi Suite might be preferable here, rather than waiting for the OTA update to hit your specific handset. For now the Symbian Anna update, which takes about 20 minutes if all goes well, seems to grace handsets in places like UK, France, Italy and India, with more to follow in the week(s) ahead.
The more interesting Symbian Belle update also leaked recently for the Nokia N8, but from unofficial sources, so if you want your evolution gradual, better stick to lady Anna for now. The source has compiled the changelog that is confirmed for now, and there are some handset-specific components, like the continuous autofocus and higher frame rate for the Nokia N8, which will roll out separately next week. In the case of the Nokia C7, the update unlocks its dormant NFC capabilities.