The body DIES if it has too much cyberware installed. And you tell me there is no gray area between being just fine, and DYING because there isn't enough meat to sustain you?
Well, yes. Because there's a very strict definition of "too much cyberware," and it's whenever you hit or pass up 0.00 Essence. Period. There are options in place for a more detailed degradation (choosing to take the various immune system flaws, or a cyberpsychosis, or whatever), but any GM that just arbitrarily slapped 'em onto a player without at least forewarning them is being kind of douchey about it. I'm a big fan of adepts (a bigger fan than most, I'd wager), but there's no need to randomly hose a street sammie like that, either, in my book. Both builds come with some downsides already installed, tacking on new ones is just showing some favoritism and likely to breed player resentment. Having someone's "meat start rejecting...in weird ways" is just randomly screwing a player who has already satisfied the rules for some gear (paying the nuyen cost and Essence cost), IMHO.
There's no such thing as almost a cyberzombie. You either are (negative Essence and crazy rituals and such), or you aren't. In a world of gray morality, there
are still some very stark white/black yes/no situations. Positive versus negative Essence is one of those things, where the rules are concerned. Low (but positive) Essence has been used as a justification in the past for describing some folks as crazy, sure, but there's no rule that says it HAS to happen.
Some folks can skate on thin ice (sub-1.0 Essence) just fine, others freak the hell out and turn into slasher-flick monsters when they first get cyberoptics and some spurs installed. As far as the rules are concerned, it can go either way.