Cinematically stunning, and the best interpretation of a WW1 battlefield I've seen on screen. The subtle, but moving soundtrack also deserves a mention.
However, the dialogue is dreadful and is far too modern to be believable for the period. The two main characters are a bit lack lustre and are hugely overshadowed by the established faces like Mark Strong and Benedict Cumberbatch, who add some much needed acting prowess. The one continuous shot idea, for me, doesn't work either. It felt too compressed and unrealistic, like watching someone play through the various levels of a video game.
The film is worth watching purely for the epic visuals, but don't expect a realistic plot or in depth characters.