I saw it the other night, and really liked it. Some very nasty and ingenious bits in it.
But.....
(Spoilers follow)
Just about all the stuff with Danny Glover felt like it had been added into a later draft of the script, almost as if a studio executive really liked the script but told the writers to go away and add in some crowd-pleasing gun fights, knife fights and a car chase. You could take out the entire sub-plot involving Danny Glover, and it wouldn't actually make any difference to the real story.
Also, my dad's got cancer. I go and see him in hospital. Trust me, your average cancer sufferer isn't much up to fighting with cops and all the other stuff the killer does. Well, except for the lying on the floor and pretending to be dead for six hours bit...