This is my second time going to this fall event but I've been to the Spring event a few times as well. Each time (thankfully) I seem to get better and better pics.
That said I started out a few years ago shooting the event with my 30D then I sold that and upgraded to a 40D which was nice but this year I bit the bullet and bought the 5D Mark II which keeps impressing me with its high ISO results.
With that said the day shots were taken with my 40D and the night shots were taken with the aforementioned 5D Mark II - ISO 4000, f/5 @ 1/250th with my 70-200 f/2.8L IS (awesome combo). Who said the 5DMK2 isn't good for sports 
I almost forgot, all shot RAW and converted using the Canon DPP Software.
Here is an image I took last year as a comparison, this was taken with my 40D, ISO 800, f/4 @ 1/125th.
From October 2008 Friday night Qualifying shot with 40D at LVMS for comparison.