There are several things that I've been positively surprised about:
* Cost of living is really cheap. Now when I travel to France or Finland I feel everything is expensive there
* Berlin is very well connected with rest of Europe (trains, flights)
* The hacker scene here is great (huge meetups, etc)
On the slightly negative side:
* bureaucracy is ten years behind Finland. You still need to visit an office to get anything done instead of doing things over the browser
* Rental agencies really try to fleece you
Since moving inside Europe is really simple, I'd urge anybody curious to take a shot and stay here for a while. For example a month in some co-working space.