The (very oversimplified) rule of thumb is that a feat is typically worth somewhere between 3,000-10,000gp. (That's based on the Alertness ioun stone, Legendary Sites in Complete Scoundrel, and a few other things). The closest effect that this feat mimics is a Cloak of Resistance +2, which costs 4,000gp, with the benefit that it's not dispellable and stacks with everything. I'd say that this is appropriate for a Feat. It's something I'd probably consider on a lot of builds, useful for everybody, but not a definite must-have for every situation. I think it would end up seeing maybe a bit less use than Improved Initiative. Make it count for any of the three garbage feats in terms of prereqs, and I'd say it's fine.