My brother called me while I was in between Porter and Harvard (to ask if there was anything I wanted them to have at the house -- answer: no). He pointed out that I wasn't going to be THAT early.
30min bus to Harvard T (there was construction/traffic)
5min wait for Red Line
15min to South Station
10min wait for SL
30min to Terminal E
There was basically no line for ticketing, and a short line for security; and nine was the first gate, so it was about 10 minutes from door to gate.
So I was ready to board almost an hour before my flight is scheduled to depart.
Sigh, apparently my only Dunkin' Donuts option was pre-security :(
Edit: And 4 minutes after I posted this, they started boarding my flight :)
Edit: Open seating, huh? (Though they board by sections.)