Cam, that comment about giving a handful of gas to roost someone is so very true, its helped me too!!
As far as hare scramble racing, I raced the 500 for the 2005 season, and did well for the first year. I moved to a 250 last season, and refused to ride the 500 because I hated the handling compared to the 250. After a wet season and alot of struggling on the 250, I'm commiting to getting the 500 back in shape to race this coming 2007 season. I rode one hare scramble and one enduro this season on it, and the handling just doesn't compare to the 250, so I'm going to work on that department, as I never messed with it the few times I rode it this year. I'm a fairly big guy, at 6'2" 270lbs, I'm sending the suspension at the end of the month for revalving and re-springing. The rest of the list for me is to get an 18" rear wheel on there to get more meat to the ground, get my steering damper on, and get new triple clamps to adjust the offset, and get some higher bars. The clutche mod Cam mentioned is a good one, and also, a little tip to help is to keep on top of lubing the cable, also the T2 cables helped me out a little with a smoother pull. Make sure to get the hand guards, pipe guards, skid plate with wings to protect the water pump cover (5 minute lead went to hell because I went with out one with the wings!). I'm still deciding what I'm going to do with the fuel, I rode a whole season on the stock tank (I have a fast fuel can set-up, dumps 1.5 gallons in about 2 seconds litterally) but I might try a bigger tank, although I think I'll hate the bulkiness as I didn't even like using the big tank on my 250. But it sounds like you've already got a good start, so all I can do is wish you the best of luck, have a blast, and enjoy the looks everyone gives you when they see you with the beast!!
By the way, what series are you running? I live in the wester NY area, I'm doing the WNYOA series and a few AGP series races.