I've never been a DDI subscriber, but I do use all the updated rules. One day in an effort to save myself some time in the future, I sat down with my PHB and a pack of those little adhesive pointers (like you'd use to point out "sign here" on a document) and tried to mark out each place where there was an update.
I ran out somewhere between Warlock and Wizard.
Which sounds like it would be huge argument toward me saying that there's too many updates, but you know what I realized? 95% of them are trivial. Adding the word "weapon" before "attack", or the word "attack" between "encounter" and "power"; adding the "healing" keyword to a power that heals; clarifying that you can't cleave into the guy you just hit; making a power that cancels stun be "no action" instead of a can't-be-taken-while-stunned immediate action. Yes, there's *something* that's been changed on just about every other page, but if you look only at major changes, there really isn't that much there.
Look at fighters in the PHB: people flipped out about Rain of Blows and, more recently, Come and Get It (and it's epic upgrade, Warrior's Urging.) Those were major changes, no doubt about it, but then the detractors held them up as *examples* of the changes... but that just isn't the case. RoB and CaGI aren't examples of the changes, they basically are the only changes (of consequence) for Fighters in the PHB. And even the detractors admit they were GOOD changes! Usually they'll say "Yeah, those ones are good, but there are just *too many changes*." Madness!
95% of the errata are tiny or obvious; they'll help avoid the occasional argument over what the rules should mean or should have meant. The other 5% (let's call them "critical updates"; haha!) are solid changes; generally making powers that were way too good not to take a little less good (RoB and CaGI), or powers that were too bad to ever use a little more viable (no one argues about those changes; like when a huge number of cleric utilities became minor actions).
Would I have done some things differently? Yeah. I would have resolved the "free action attacks" problem differently, and handled all the little things that had to have a "non-minion" inserted before "enemy" differently. But what WotC has done works just fine.
Is the game fun and playable with no updates? Sure is, and if you don't want to bother with them, rock on. But it's even better with them, and usually the only argument you'll have with anyone goes "That killer thing you've got, the one that seems too good to be true? Yeah... it's no longer true."