First off:
Rule 0 is all-mighty, all-powerful, all-everything. Rule 0
can beat Elminster. If you don't want to buy a d20, Rule 0 says you don't need it. Rule 0 says you can get a duck and hit it and if you like the noise you succeed, if you don't you fail (bonuses are how many times you can hit the duck; penalties means the duck hits you.)
In other words: It doesn't matter whether or not you like the new rules, because no one's forcing you to use them.
Now... The one potential problem I can see is that if you don't like the rules, you have to convert a certain amount of new stuff (which, incidentally, is totally dependent on whether or not you LIKE that new stuff) back to 3E. That can be a pain, it increases prep time a little. Or, if there's old stuff you like, but you like 3.5e as a system, same problem but backwards (but why are you complaining about the new system if you like it?)
In short: If you buy a new supplement it will take you more time to implement it into your game. It takes time to implement it into your game already, but more, you know. And that's not entirely fun.
This will happen with every revision. Be happy it's in small steps: That means that if you want to keep up, you can do so without any staggering transitions, and if you don't want to, it'll be a while until new supplements are no longer useful to you. (Believe it or not, "RPG technology" does evolve, and it can become obsolete. Why wasn't 2e made like 3e in the first place? Consumers thought about the game differently, and further, they thought about
things differently... The task resolution scheme of the d20 system is essentially an object-oriented programming environment: It is modular, hierarchical, and I have no doubt this is more than just coincidentally similar to desktop computing systems... but this is a major tangent, and possibly worth a thread of its own, but nah, never mind

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