Game has ran extremely smooth for me as well. I do also experience the random freeze up for a few seconds. Seems to happen when destroying towers and/or the stronghold of the opposing team.
I have tried on both my systems:
Mac Pro: 2 x Intel Xeon 5482 @ 3.2 GHz, 6 GB DDR2-800 (FB-DIMM), 8800GT 512MB, Windows Vista x64 SP1 (Res: 1920x1200)
Runs perfectly maxed out on this system.
MacBook Pro: Intel Core 2 Duo @ 2.33 GHz, 3 GB DDR2-667, ATI X1600 Mobility 256MB, Windows Vista SP1 (Res: 1440x900)
Have to tone it down a bit, no AA, and pretty much everything on medium, but it runs great under those conditions.
I'm extremely impressed with the performance of this game. I can't wait to test in on their online system, but hamachi/LAN games work for now. Keep up the excellent work GPG and Stardock.