I went to see it last night, on word of mouth recommendations, and I enjoyed it very much & more than I thought I would.
I understand why some would be put off by the 'history film' aura, but it's not like that. It's a genuinely 'humane' film about one man's struggle with his failings, when he's made a very public figure with no hiding place.
Some other things I liked :
1) Cinematography is not bog-standard. They use muted colours with natural light effects & use a lot of angled shots (eg brief glimpses of buildings looking upwards, or looking up at characters), shots with single character off-centre, gives more of an interesting feel to it. It looks at odd little details, which I can relate to.
2) Family conflict, in a very repressed-but-acutely-painful way. Anyone who's been there on any level can relate.
3) Didn't get boring - kept it moving.
4) Humour - dry, liberally applied. If nothing else, go to see it to see Colin Firth do a line in continuous swearing (this was part of the therapy btw!)
I found it a funny, sad film and made me think about the sort of lives those who lived through the two WW had. Makes me grateful once again for what they did.