Set an alert for an event in a subscribed calendar in iCal

Keyboard shortcuts: Mail has it's own keyboard shortcuts, which you may have to learn.

Alternate email addresses/multiple accounts: works fine. Don't know about plus-addresses.

Priority inbox: this is not supported. Labels work, as does flagging. Public calendars work in iCal.

Syncing is very easy to set up - via IMAP in Mail, and in Preferences in iCal. In Lion it's even simpler.

Yes, you add each account separately in mail. You can still visit them in any browser or device.

To set single alerts on all birthdays, you can avoid a script altogether:

1. Open Calendar Preferences in Calendar.
2. Under General, tick "Show Birthdays calendar".
3. Under Alerts, set an alert for "Birthdays".

I haven't taken the time to actually write up an AppleScript for the double alarm parts, but this article seems to cover scripting calendar alarms quite nicely. I would imagine you would just need to create a file or list in the script that contains the names of the events (which you can deduce from the standard naming convention Calendar app uses).

Also I am using Mountain Lion with Calendar app. I can't recall if the steps above work on older versions of iCal.