I just finished up my 3rd or 4th box of this brand. It's approximately 13% protein. (grams of protein divided by grams of flour; 4g/30g = .13). As you might have guessed, there's 4 grams of protein to each 1/4 cup (30 grams) of flour. You can find additional nutrition information at Hodgson Mill's website.
When compared to all-purpose flour, I found it quite good, but still not 100% "pizzeria taste" because you'll notice the bread flavor to some extent. The contributors here seem to know better than I do about the available flours, so I'll take this US retail-available item for what it's worth and recommend you try it anyway.
On the other hand, after reading the forums here recently (thank you, people) I managed to find King Arthur Unbleached Bread Flour (also with 13% protein - 12.7%, according to their web site) at the same store (Redner's) that carried the Hodgson Mill. For about 50 cents more, you get a 5 lb bag instead of a 2 lb box/bag of the HM. KAUBF is also 4g of protein to a 30g (1/4 cup) measurement. I will be trying my first pie tonight and if it's NOT as good as the HM, I will post later. Yet somehow I doubt I will after reading so many good comments here about it.
From what I've read here recently, one of the "ultimate" flours the consumer can find is generally regarded to be King Arthur's Sir Lancelot Hi-Gluten Flour, a 3 lb bag you can order from their web site. KASLHGF is 14.2% protein, according to their web site.