Tying into the past is okay. Being irrevocably hog-tied to it without the ability to change a single thing is very not so cool, for my two cents. What's most important for me is internal consistency. Realism in a game is an odd concept. Do the changes fit within the general guidelines that the previous material has established? Does it push the envelope without making it unrecognizable from the previous material? Is it internally sound material, without contradicting itself? If it contradicts previous source material, is it done with an eye to explaining the differences and keeping those changes from being confusing?
So long as those sorts of questions are asked, I don't see any real problem with change. It's necessary for the game to move forward, and the direction it will move forward is going to change under different folks. I didn't like some of the initial changes made under Rob Boyle, but came to appreciate where things were headed with SR4. I'm fine with change, so long as it hangs together and remains internally consistent. Changing something "just for the rule of Cool!" isn't always the best idea, if the consequences of said change aren't at least glanced at. The rule of cool has always just seemed like an excuse to me. I'll really be looking forward to Attitude, providing the editing/proofing issues of WAR! have been addressed. (I seemed to recall reading in one of the multi-page threads here on Dumpshock, those issues had been looked at.) It was a little disconcerting to see recent BT material not suffer from the same editing drop-off that recent SR material seemed to have. So if those things are addressed, I'll be glad to look at more material to see if I like the direction SR is headed in now.
WAR! wasn't something that really rang my bell, but to be fair, neither was fields of fire. Or the military gear in Arsenal. I don't really have much interest in the military side of things in SR. I'm here for the criminal/media aspect of the game, and get my military fix in other games. I still purchased it and read it, as I like reading new SR material (just a bit more difficult reading for me, because editing problems is a personal pet peeve). Attitude is definitely subject matter that interests me in SR, though. Here's hoping it's a good read!
Edit: Please don't have Attitude start off lacking an introduction. That was an unwelcome surprise in WAR.