This is a surprisingly good show. The visuals are excellent even with liberal use of well done CG of destroyed Berlin. The story is well done and moves at a quick enough pace to keep a modern audience engaged. The history is excellent.
While the main story is fictional, the show constantly comes up with things that few people know about today such as the Jewish Hospital that openly operated in Berlin and survived the Nazi downfall. There is a book about the hospital called Refuge in Hell by Daniel B. Silver.
Berlin was as dangerous as the show portrays and the Russian sector the most dangerous though the late 1940s (at least for any German). However, there are a few things that might be a bit off putting such as some of the uniforms, in particular the US uniforms. Most of them are ok but some of the US helmets (more poor helmet liners) look like kids toy helmets, in particular the 45th Infantry Division Major General's helmet. Some of the materials for the enlisted uniforms also look a bit off but It might just be hard to get those original cloth materials in today's world. (Though Band of Brothers seemed to do an excellent job.)
Some (not all) of the attitudes of Germans may also be a bit too tolerant for the time. My dad was in the Army during WW2 and following combat worked the Displaced Persons (DP) section in Bremerhaven post war. Many Germans were not happy about losing the war and showed it in various subtle ways.
One example of over tolerance is how the character playing the 16 year old Jewish kid working in the police station is treated. I do not think he would have been quite so quickly and comfortably integrated with Berlin Germans given 15 years of constant anti jewish propaganda so soon after the war. However, the use of so many German women in various rolls was likely more realistic given the German men were still in prisoner of war camps all over Europe.
If you are not super critical these items do not take away from the storyline.
I have seen 4 episodes so far and all of them are very good and seeming to get better. I hope this has more seasons.