I was thinking about doing that one- but opted for the 5 day instead. Everyone I talked to that went on it had a blast and said it was the perfect amount of time. I'm probably going to book the 3-day London trip before Oktoberfest and then head to A'dam after Oktoberfest.
Im doing the 7 day Oktoberfest this year... considered the 5 but then decided for little extra cost and the fact that the 7 day gets you to the opening - i thought why not!