A great cast in a decent series but not one without limitations. Whats very likeable about this series, is, in a sense, also its key shortcoming.
Jeff Bridges who plays the main character a wanted CIA spook, is possessed of a downbeat, affable quality that belies the mans deadlier qualities. The result is when he is forced to transition from one persona to the other, its a discordant experience. This is, I suspect, just what the writers wanted and its a ploy that works beautifully. The harsh transition from harmless and friendly to fierce, captures your attention and holds it.
Its also what does not work so well. The old man stereotype with a range of ailments, popping pills and walking stiltedly, is overplayed. So much so, that it somewhat undermines the deadly assassin alter ego. You start asking how a man portrayed as this enfeebled, could take on and defeat trained men half his age? Of course, in hand to hand he probably couldn't and whilst this is suggested, at the same time the series is still pushing this premise. The presence of two attack dogs is supposed to help explain this away too but in actuality, their actions, create, at times, implausible plot holes.
This series would have worked a little better is the "old geezer" aspects of the character had been downplayed a little more and the mans years of training and experience, was given more emphasis.
That said, there is a hell of lot more to like here than not. Its an enjoyable romp, that's comes armed with decent writing and as I said, a great cast. Action is well paced and the improbable elements of the story don't stop it from being fast paced and enjoyable. Mixing as it does clever dialogue, well rounded characters with lots of violent exposition.
8/10 from me.