It's very noticeable on a slower weapon, like a Pike. Having a higher WPF for the weapon lets you block quicker, recover from weaponstun faster, finish your blocking animation faster, etc. People who rely on tap-blocking might be surprised when their weapon doesn't hold the block for as long as they wanted when they get a large boost of WPF because of this.
Edit: On the other hand, I might be confusing the attack speed benefits that WPF gives with faster blocking; I've always noticed a difference in my blocking speed with higher WPF, though, especially against multiple opponents.
