The main thing I hate about CHs are that they disregard all stat-ups, which really fucks shit over. I don't mind the damage boost, but it seems like every three battles, my opponent gets a Critical Hit on my Curse-Lax. :-\
I'm the other way around; I wish they didn't do extra damage, but am grateful that they punch through stat boosts in the opponent/stat reduction in the user.
Earlier today I was battling someone's Gyarados whose attacks where presumably Waterfall and Earthquake with my Dragonite (one that knew roost, BTW); my opponent's Gyarados that DDed on the switch waterfalled for a critical hit doing ~56%; it then waterfalled me again, getting a second critical hit scoring the KO...
:chaos:
I wasn't particularly grateful that my opponent had to get these crits twice in a row; if either one wasn't a crit, my Dragonite would have survived (and as it didn't taunt presumably would have been able to roost/t-wave) easily.
Oh well...
However, in the case of defense boosters-they give the opponent a chance to still win, can end stall wars, and really in my opinion balance the game. This is a statement coming from me despite myself constantly using Curselax in the online battle tower, and getting frustrated whenever the AI gets a crit breaking through my defense boosts for the KO... In situations like this I really believe that critical hits might be helpful, although most teams run (p)hazers.
I guess I agree with Obi, although he states that even without them defense boosts wouldn't be an issue.
EDIT: about my story where the Gyarados scored two crits in a row letting it take out a pokemon that otherwise would have walled it; I was otherwise losing the game if I remember correctly so it didn't necessarily cost me the game, however, assuming the rest of my team was better an incident such as this could have been quite critical, and obviously extremely "hax".