I never saw the point in buying 3rd or 3.5 myself.
I'm one of the dinosaurs that can do algebra

I've looked at 4thEd and I can say I think it's a step in the wrong direction. The idea that evil is winning and alignment is not as rigid as it used to be seems to me that the designers of the current system are dumbing down the game. For me, alignment was self explainitory, it made sense, it wasn't ambiguous. You didn't need to do a university unit in ethics and philosophy to understand it yet the way some people over at WoTC carry on, you'd think that they always hated the alignment system.
In regards to the idea of change being good, well it depends. Yes change is ineviatble, that's a constant, an undenyable truth. However not all change is actually warranted. I think that the axiom of "if it isn't broken, don't try to fix it" springs to mind here.
My friends bought into 3.5 and I played in their campaigns and now they are dismayed by having to learn a new system all again of they wish to stay upto date with the current system.
What it all comes down to is you and your group and what you enjoy. WoTC doesn't have control over your imagination and that's what D&D is all about in the end, a game where your imagination can run free. In my 2ndEd campaigns, house rules over rode silly inconsistancies in the rules. We used a mixture of 1st & 2nd Ed and it worked fine because the systems were compatible.
Sadly though it appears that they made 4thEd to be a new game totally which means that any previous material you have is sadly worthless if you wish to incorporate it into 4thEd. I suppose campaigns and modules could be used but they'd take a heap of work to convert and that sort of defeats the purpose.