It's not just HDR - it's all of the effects that DX9 cards will do. Plus, it's just plain faster than a 9800 anything, so it's a win-win.
Look at the Lost Coast reviews and pictures. Seriously. It effectively makes high levels of AA unnecessarry, because the most important environmental effects render perfectly. I notice smoke, fire, light, and so on much more than slight graniness around the edges. It works so well, IMO, that 2xaa is all you need. Aniso filtering can also be bumped down a notch. Not all games use all the features, either. Many games use the water transparency and blooming only - it's not a checkbox feature - you just can't see it rendered properly with an older card. Very much like comparing a DX6 era card to a DX8 when it comes to smoke and fog.
Even then, it still isn't a dog - it gets 48fps @1024*768 with 2xAA and 8x aniso AND all the HDR effects at once. Dropping aniso to 4x should be enough to get ~60fps in most games, which you can't get out of any previous generation card. Without HDR, it lays down times very close to a stock 6800. With everything enabled, it's faster than his current card with nothing at all turned on.
Try playing Fear on a 9800 Pro. It just isn't up to the task without practically turning on line-doubling, yet a 6600GT is if you keep it down to more reasonable settings.
For the price, it's a steal.