I'm pretty sure I'm the only person I know who didn't hate Arrival. Sure, nowhere near as good as Shadowbroker or Overlord, but I felt it did a nice job building up some more dread for Harbinger, plus the obvious plot twist for Shepard. Whats more, I'm never gonna say no to more things to do in ME2, even if the whole thing with the Artifact was groan-inducingly easy to predict.
EDIT For Sparda
Shepard blows up a Mass Relay to stop a surprise Reaper assault, Which just so happens to be in a populated Batarian system, which kills them all, since Relays apparently go off like Supernovas.