Hannover was my 20th marathon. All-in-all it was a good experience. Beforehand, I expected little crowd support, but the sunny weather helped to draw the people out of their homes. The police reported a total of 100.000 spectators. There were many cheerful senior citizens, every now and then a drumband and, in the city center near the finish area, even large crowds.
Although it was sunny all morning, the heat was bearable, partly because there was some shade most of the time. The course was very fast (PR-material with only two not-too-high bridges and some sharp curves to slow you down) and offered enough variety for my taste. The only section I could have done without were the tough kilometers 36-39 through the pretty but spectatorless Herrenhäuser park.
The organization was adequate, nothing fancy.
My conclusion: a friendly and fast city marathon. It's probably not the right choice for those who will run a marathon only a few times in their life (for those I recommend Berlin, Hamburg of Cologne in Germany), but for others, it's a fine, worry-free choice.

If the weather is nice - this year 2005 there cold wind but sunshine - this is one of the best marathons. Very good organization, plenty of drinks and food along the course, very good massage...

It was my fifth marathon and my fastest (3:24:11). Only few spectators along the course. Near the finishline some more people. Next year I will start again because I'm living here.