Your choices have matter and impact how the story develops. Combat is ok, quite same as in second game. Oh and its a long game, especially with the two story dlcs. There is lots of replay value in this game, but knowing how long it is my second playthrough won't happen very soon....:)
I have played old syndicate wars (second game in the series i think) and this game has lots of the same things that one did. There was bit more story in the old one with its missions based campaign. But in these games the main thing is (to me) to research new tech to edit your arsenal so you can infiltrate the more difficult sectors on the map. A bit more destructible environment would be great though. Tip. be sure to take the support agents time slowing skill early, makes fights a lot more enjoyable.