I think the album is solid overall. There is only one song I don't like (When The Eagle Cries), and one mediocre one (Hollow Man) which is still good, and the rest is good to awesome. I think Gettysburg is fan-bloody-tastic, and one of the best things the band has done. Right up there with Dante's Inferno and The Phantom Opera Ghost.
I think Owens sounds great also. At first I was VERY skeptical, and all 'bring back Barlow', but I think Ripper's voice REALLY fits the music, better than I ever imagined. On some songs, like The Reckoning and Red Baron, he sounds incredible, and he does a fantastic job on Gettysburg. As much as I love Matt's vocals (he is incredible on Burnt Offerings), I don't think he could have done TGB any better than Ripper.
As Spawn said, if you like older Iced Earth, you will probably like it to some degree, but I also think you can like it without liking older Iced Earth as well.