In this case he's talking about video calling. Ignoring the fact that nobody is actually going to use video calling (it has come so many times on many devices. The Evo was far from the first device to implement it), let's humor his point.
So let's compare-
Apple iPhone 4 - video calling between iPhone 4 devices, only over wifi, using Apple's completely new, completely non-standard protocol. Apparently it "works great", at least for people using demo units at an Apple conference under controlled circumstances.
Evo 4G - Android device with a front-facing camera. Apps support it to talk on any network you want. Fring, for instance, allowing you to call Skype video users on pretty much anything including PCs. This is over wifi, or a 3G/4G connection that can support it.
Gruber has close to no experience with the iPhone 4G, and his entire experience with the Evo 4G is one reviewer's take. Nonetheless, that has made him an expert.
Is iPhone 4 to iPhone 4 calling considered done? Seriously? To me that barely qualifies as beta. It barely qualifies as alpha. There are a legacy of long existing, open video calling protocols, and many existing implementations. Only the truly faithful could call Apple's take done.
EDIT To draw from a comment I left elsewhere, here's an exercise for Daring Fireball supporters: Imagine, if you will, that Motorola just introduced their latest Android device, front-facing camera and all, called the iDroid. The iDroid comes with an easy to use, ultra-simple video conferencing solution, but it only works on wifi, and it only works between iDroid devices.
How, I ask, would John Gruber respond to that? Imagine that it's been tightly polished and all.
Would he post a praise-filled entry lauding their innovation, heralding this great new functionality? Maybe I'm just being a jerk, but I think he would viciously attack it.