I enjoyed it, but I felt a little let down. It was too hard to not compare it with the book or, more tellingly the series. Where it triumphed was the great dreary 70s period setting and look-it is an exquisitely designed production, and the great British cast Swedish director Tomas Alfredson put together.
Watching it again today - I'm a completist, I couldn't resist the DVD - I'm pleased to say I can now appreciate it on its own merit.
If you haven't come across Smiley before, I urge you to watch it. If you have, I urge you to watch it too, but with an open mind. And maybe watch it again.