They are normally priced between $10-$20 so there is not that much risk involved when deciding to buy a downloadable game over the PSN and Xbox 360. But I usually make sure I play the demo first before I purchase the game just to make absolutely sure that I will enjoy the game.
I have purchased downloadable games over steam as well. The process is pretty simple to get used to, but I did have one bad experience. I downloaded a game that constantly crashed on my PC (Call of Juarez: Bound in Blood). So when something like that happens you're pretty much stuck with the game. If you had a physical copy you might be able to take it back to the store and get a refund. But Steam said "No refund for you...sorry".
The main reason I watched was for the exclusive world premiere trailers and not for the actual awards which makes the whole show rather pointless. Since I do not get SPIKE I tried to watch them online with the 4 different camera angles which turned out to be a frustrating experience. Hey camera man! Remember to keep the camera pointed at the screen next time so I can see the damn trailers!
I've been to three midnight launches so far (Halo 2, Halo 3, and GTA 4). All three went pretty smoothly. I showed up around an hour before midnight and stood in line and I usually made it home before a quarter to 1 AM. I do so because there is always the fear I have that my copy will not be available if I wait until after work the next day and attending the midnight launch and buying into all the pre-launch hype gives me something to be excited about. However, when I do purchase a game at midnight, I only can play the game for about 30 minutes and then go to bed which makes the whole thing kind of pointless.