That was one of my favorite parts of the game! The scale of that battle was epic. I wish that Fallout had more battles that were that size, but the engine can only handle so much. The game would frequently crash during that battle as it was.
I loved that battle. I was so impressed that my PC was able to handle it, and I have a fairly new rig so it's not like I was playing on a toaster. Hopefully they'll surprise us this year as well!
It was fun but it would be sweet if you could use him during more battles. It seemed really short lived! I want to be able to operate him just wandering the wasteland. It would be pretty cool to blast a death claw away with a huge tesla cannon.
Liberty Prime is absolutely one of the biggest highlights of Fallout 3. It definitely made the final part of the game that much cooler.