I'm a little late -- I just purchased Sins, and this was my experience with Impulse.
- Downloaded Impulse and installed it. I really didn't like that.
- .NET is required. I didn't like that.
- IE 7.0 is required. I didn't like that.
- I got everything installed and ran Impulse and it worked. I liked that.
So, there's good and not so good. Impulse did what it was supposed to do, but I also know that I can buy Corel Painter X for $378...as I discovered clicking around the Impulse interface. Clever idea. Convenient, nifty, quick...I might even use it some time. But, I didn't necessarily want to install that onto my PC just to download a patch for one game.
There's not much harm in it, but I'm not thrilled about it.
How about using the same method as Blizzard? Their torrent patch downloads seem to work pretty well.