Joy... "Twitter is deeply integrated into Mountain Lion". I don't use FaceBook and I don't use Twitter because I don't want to. Granted, I still won't "have" to use Twitter, but I'm going to be forced to see it all over.
How so? Twitter is integrated into iOS 5, yet you would be hard-pressed to notice that fact on a day-to-day basis. Heck, I use Twitter myself, and often forget about that integration. You're worrying yourself prematurely about something that is unlikely to be an issue.
BTW, you might consider trying Twitter. I personally can't stand Facebook, and still don't get the whole social media thing. I find no need to tell people that I just ate a ham sandwich or walked the dog, and certainly don't want to hear such information from other people! But Twitter has proven itself to be extremely useful for browsing stories from selected news sources. (I follow MacWorld and MacLife as well as a number of security companies, for example.)
GateKeeper... although not really an issue as it is now, I can already see the day when we'll need to jailbrake our Macs to install non-authorized applications.
Again, you're making up things to worry about. Why would Apple build an entire infrastructure of OS features and servers, allowing developers to verify themselves without having to put their software in the App Store, if they intended to force developers into the App Store? That makes no sense.
Us old timers haven't really been happy with the direction things have been going since Lion.
Speak for yourself. I'm an "old timer" - I've been using Macs since 1984. I like most of what was added to Lion. Most, not all, but the same would be true of pretty much any version of the Mac OS.
I've been hearing complaints like these almost since 1984, and I won't take them any more seriously now than I did 30 years ago. Most people never like change, and never want to learn a different way of doing things, even though those new ways of doing things might actually turn out to be better.