As terrorists, were they a success?
Those who study such things know this: the whole point of terrorism is to terrorize, not necessarily to kill.
The consequences of being terrified are to hole up, get defensive, and become irrational. Boston shut down. The city went into basically martial law. And TANKS armed with 50 caliber machine guns on turrets patrolled the streets of Boston, looking for one man. ONE MAN!
These guys were just as successful as OBL, but with far lesser means.
So, were they successful as terrorists?
Argue that they weren't.