My first books were Eisenhorn/ravenor, Gaunt and Cain.... all non marine ones, with characters I really loved, they had substance! From Jurgen with his endless cups of recaf for cain, to try again bragg who i literally shed a tear for!
The Heresy books have been good, some great ones, but most are good. Ive only read the iron warriors/ultramarines omnibus, and the armageddonADB 40k marine books because i keep hearing about the lack of character in a lot of the marine focussed books. Guy Haley isn't the best i must say, but he seems to have a good contact at GW and they keep selecting him to do more writing.
If McNeil had done some of these newer books I can see there would be a slightly different tone to the conversations on here and other forums.