Does anyone here use the St. Augustine's prayer book, or even the St. Gregory's (Ordinariate)? What do you think of them? If you have experience with both, how are they in comparison?
I like the St. Gregory's one. I haven't seen the other. I'd suggest the Gregory's one is worth buying.
Avoid the 2014 Newly Revised edition of St. Augustine's Prayer Book (a large amount of content was cut, the language dumbed down, etc.). Both the 1947 and 1967 editions are solid prayer books. The 1947 has nicer artwork for the stations of the cross. St. Augustine's Prayer Book and St. Gregory's are both very similar. The biggest difference is that the St. Augustine has longer morning and evening prayers and the St. Gregory has a few more litanies. The St. Gregory's also has updated language to align more with the RCC's sacrificial understanding of the mass.
Here is a good resource for the 1947 edition as noted by Spiritus: https://anglican-parishes-association.myshopify.com/products/st-augustines-prayer-book