The book series I found was enjoyable, and I've been liking the TV show for what it is...
That said, a lot of little things bug me (Beocca as a bald normal-looking man instead of a palsied redhead? Alfred actually being a half-decent warrior? A greater focus on Uhtred's militant defense of his paganism? Serpent-Breath being way too ornate? And of course 2/3 of Book 1 being covered in the course of the Pilot episode). That said, I can watch, and truly enjoy it on its own. Just not as an adaptation of Cornwell's work.
G_Los also hit on a lot of the toher things that annoyed me. Uhtred was TAKEN to Eoferwic to learn how to be a proper ruler...not hidden away because he's the 'future' of Bebbanburg...and I was hoping for a rather impressive setpiece battle where the Danes draw the Saxons in through a broken section of wall before being trapped from two sides...
Eh, again, good stuff, just not a terribly faithful interpretation of the novels.