Oh, buying games online is fantastic.
1. There's only two places here (Maui, Hawai'i) that sell PC games - Walmart and Gamestop. I'd much rather buy from Impulse/Stardock and Steam/Valve as I believe they're far better for the industry. I try to buy locally as I can, but this is definitely one of my exceptions.
2. No more lost/damaged discs or registration keys. Very convenient. I recently moved off of Windows 7 RC to Windows 7 Home Premium - using Impulse I reloaded all my games, fully patched, without having to fuss with much at all.
3. I love the sales. Brick-and-mortar stores almost never have sales on games that I can think of.
4. Indie games, old games, and more! Retail is pretty ruthless, and there's some great games that would probably flop horribly in a retail environment if they even managed to get carried at all. Digital services like Impulse are fantastic venues for them.
I've bought apps from Impulse before (Windowblinds, Objectdesktop), but by and large? I buy games! I'd love to see more apps come on board, naturally (FRAPS would be a good one to see here), but for games Impulse is defintely one of my go-to places.
I'm eagerly awaiting Beat Hazard to come to Impulse, and am highly tempted to rebuy Devil May Cry 4 digitally so I don't have to worry about my disc anymore (the retail game requires disc in drive).