I played the demo of Splinter Cell Double Agent. The thing was a trainwreck. Double Agent utilizes some of the worst multiplayer networking ever coded, making the demo nearly unplayable. I must have tried about ten times to get into a game when it was a relatively new demo and it was just no luck.
I ended up buying it anyway knowing the Splinter Cell series is sure-fire for the multiplayer (I was right) but if I had never seen anything from Tom Clancy's Splinter Cell before and that demo was my first exposure, I would have blacklisted the series immediately.