Refer to the productapi post for comments.

  Version allowed in cart attrib­utes adjust_­price adjust_­sub­product_­price cart add item delete fields form insert load on payment complet­ion subproduct_­types transac­tion update valid­ate wizard_­select
Documentation:
hook doc(code) 1.9.2.1   x x   x x x   x x     x x x x
hook doc(comments) 1.9.2.1   x x   x           x x x     x
ProductAPI users:
cart 1.133.2.13 x       x                      
product (invokes) 1.116.2.17   x x     x   x x x       x x  
store (invokes) 1.125.2.23                     x   x      
subproducts         x               x        
Actually used   Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes No
ProductAPI implementers:
cart 1.133.2.13           x                    
contrib/apparel 1.6.2.1   x     x x x x x x x x   x x x
contrib/auction 1.19.2.3   x x   x x x x x x       x x x
contrib/coupon 1.6.2.2   x x               x   x     x
contrib/donate 1.9.2.1   x x   x                     x
file 1.37.2.7   x       x x x x x       x x x
generic 1.8.2.1   x                           x
parcel 1.27.2.3   x       x x x x x x     x x x
tangible 1.21.2.2   x     x x x x x x x     x x x
Actually implemented   No Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes