I would say its a moderate problem - It's not going to kill your card to have it like that, obviously, however it will help a lot if you were to lap it. And in all honesty, if you're running this on stock, don't bother unless you're REALLY bored. If you're going to overclock, I'd suggest a heftier solution than the stock.
Lapping is the process of basically sanding down the bottom of the heatsink on a very flat material such as glass, to make the heatsink flat and free of ridges. The flatter and better contact you get with the core of the Radeon GPU, the better the heat will get off that chip. This could extend the life of your precious card by keeping it nice and cool.
You'll want to start with a 400 or 600 grit wet sandpaper, add some water and a drop of dishwashing liquid (some reccomend the diswashing liquid to reduce sticking to the sandpaper... personally, I didn't have any problems with just straight water). Then, take that 7000 heatsink and push it away from you, pick it up, and repeat the process (so you're only going to go in one direction).
Also, you can take a sharpie to the bottom of the heatsink and see if it is truly flat - make and X on the bottom and start lapping a little. Check to see if the X is wearing off evenly, or if one corner isn't quite coming off. If its not wearing evenly, you can visually tell that your heatsink isn't as flat as it could be.
Then after that, some people like to use some higher grit paper, 800 grit works great (and if you want a mirror shine, go even higher progressively) You should be able to find the super-fine grit paper at auto parts outlets (Think PepBoys).
Then you should be able to get rid of those ridges that inhibit the heat from transferring as efficiently as it could, and rest assured that your Radeon will be thanking you for the pampered service!
HTH!
