I just finished Broken Sword: The Angel of Death and I'm having mixed feelings about it. I loved all the locations and characters in New York, but I felt that the game got steadily worse after that. Some of the last hacking puzzles drove me insane because the game didn't explain all the new factors, and I didn't think to check out the manual.
The ending plain sucked. If it had been different, it might have saved a lot. What I especially missed was the well developed characters. I felt like there should have been more dialogue and background info regaring the different characters. Spallacci, for example. All in all, this is my least favourite BS game.
I heard the game sold quite well for starters, so maybe there's a chance for a fifth some time in the future. I wouldn't object. I refuse to believe that the series ends like this.