Jennifer Hale did not voice Cortana. That would've ruined Halo for me.
Jen Taylor was very good.
Speaking of Halo (and Uncharted...and Mass Effect's EDI), got to love the ODSTs too.
I remember seeing a preview for ME2 and thinking Yvonne Strahovski might be terrible (the line they show her delivering was thankfully not the take they used in the final game) but I was surprised at how good she was. I mean, I usually find 'typical' Australian accents annoying but I love her voice. At that point, I had not seen Chuck so I had no idea that 'cold and distant, with occasional moments of warmth' was what she had been doing for a while already.
Can't really fault any of the Mass Effect voice cast, I even liked Zaeed.