On the "these feats are too powerful" issue, consider this:
I think the vast majority of the feats in D&D are too weak, too boring, or both.
Historically, we've been way too conservative about creating exciting, potent feats. We've spent way too much ink printing feats that give you a small numerical bonus (often only applying in a corner-case game situation), and not nearly enough creating new equivalents of Cleave and Spring Attack. PH2 represents an intentional shift in that mentality.
The other tricky issue is that unlike, say, spells, feats don't have an easy ranking system to compare them against one another. If Spring Attack were a "4th-level feat" and Toughness were a "0-level feat," it'd be easier to see how much better the former is supposed to be compared to the latter. PH2 has a lot of feats that, due to their high prereqs, are effectively "high-level" feats, and thus are very much intended to be more powerful than those that've come before.
Some folks will freak out when they see what's available in PH2. I think that's just flat-out a good thing--it's about time folks got excited about a new D&D book