I recently bought an Efficiency 5 Unbreaking 3 Silk Touch 1 diamond axe and it's the same speed on pumpkins and melons as it used to be before the 1.4.6 update. The only mods I have are CJB and optifine so I don't have any sort of fastbreak mod activated. Other people say their axes don't work so I really don't know what's wrong.. Thank you
Nothing is wrong. I have the same speeds you are saying you are experencing happening to me. Eff. 5 axes just go really fast. (Unless we both have something odd about our crop harvesting speed.)
As far as I know pumpkins stayed fast, but melons were considerably slowed down. Maybe you got lucky and your axe wasn't affected