Anyone who is a fan of any of the previous Silent Hunter titles will find this a BIG disappointment. It's all eye candy.
I will quickly mention the very contentious issue of using DRM to play the single player game. This for me is not a problem in itself, however, within only 3 days of playing this game I have had several problems with logging onto the Ubisoft servers including delays of upto 10 minutes (that's not an exaggeration) and in some cases I have given up completely to return later to try again. Also, your saved games are stored on thier servers too and I have had some minor issues with the games being saved correctly (i.e. a sunk ship has reapppeared).
On the positive side the game looks awesome with some wonderful weather and environmental effects. The ships and the u-boats look great, there is much more contact with other friendly vessels (including other u-boats). Also you can now walk about inside the u-boat where there are crew memebers to talk to if you wish.
But that is all that is improved over the previous games. Unfortunately the UI has been radically changed for the worse. The method of steering the u-boat is terrible. There is no longer a compass to hand for you to select a bearing or direction and has been replaced by a point-and-click system which doesn't work if you are submerged - very frustrating if you are trying to evade a destroyer. The ability to walk thorugh the sub has become a pain as now you HAVE to walk through the sub to get all the reports you want (depth under keel, radio reports, sonar reports etc). Very very frustrating when you're trying to evade a destroyer! Someone has written a review that this is what a real u-boat captain would have done. No he wouldn't! He would shout a command and the report would be given to him - he would not be expected to leave his station.
The targeting system has also changed and is now more like point and shoot (like using your periscope as a gun). There is a feature now where you are able to walk through the sub and chat with the crew. Sounds like a good little addition to the game doesn't it? Wrong! It is a pain in the *ahem* because it is not just something you CAN do it it something you HAVE to do becuase you raise the morale of your crew by talking to them. Is this something they added to please the RPG fans out there? It has no place in a Submarine simulator. Asking the same crew member how his family are time after time after time is just plain wrong in this game.
One other thing to mention is that the AI appears to be worse than previous titles. I have noticed that it is very hard to get spotted, riding on the surface at full speed and still didn't get noticed by a destroyer on my flank. I had to shoot at it for them to see me.
In fact there are far too many things to list on here what is wrong with this game. Look on the official SH5 forums, there are plenty of people on there spouting it all off.
It is also very buggy. Certainly it does not appear to have been tested very well but I suspect (hope) these will be rectified with patches.
To summarise, this game is all eye candy and it appears that this is what Ubisoft is using to sell the game. The game itself is very frustrating due to bugs and poor design. I'm going back SH3. It may not look as good but it is a much more enjoyable experience.