Crysis Warhead
Rather than use a timedemo, I tested Crysis Warhead by playing the game and using FRAPS to record frame rates. Because this way of doing things can introduce a lot of variation from one run to the next, I tested each card in five 60-second gameplay sessions. The benefit of testing in this way is that we get more info about exactly how the cards performed, including low frame rate numbers and frame-by-frame performance data. The frame-by-frame info for each card was taken from a single, hopefully representative play-testing session.

We used Warhead's "Mainstream" quality level for testing, which is the second option on a ladder that has four steps. The "Gamer" and "Enthusiast" settings are both higher quality levels.

Obviously, this game puts quite a bit more strain on the GPU. The 4830 handles it with composure, basically matching the GeForce 9800 GT. With frame rate minimums around 25-28 FPS, both cards run Warhead quite nicely at these settings. I enjoyed blowing stuff up with each.