Although previously I have discussed clicking speed not being important after the first hit, 1.8 seems to change that. In 1.8 if you click above 15-20 cps it will not let you. I believe this is because the developers have implemented a sort of click timer. This click timer will now allow hits to register more easily the faster you click, up to around 15cps. Going above that will cause a glitch. This is a problem when it comes to hackers however. All we really need is some client to figure out a way to bypass that and rip we have 1.5 pvp on our hands again. Getting the first hit is still important though. If you get the first hit in 1.8 (due to faster clicking than the guy you're fighting) your reach is automatically extended by 1/4 to 1/2 of a block against all people until you relog or the it wears off (not sure the time). Now if you miss the first hit or swing your sword before fighting the enemy or look at the ground your reach literally goes to 1-2 blocks maximum for the rest of the game and/or when you relig/it wears off. When experimenting you will not see a difference until you actually fight a person. This is the reason stuff lile this can happen:
Just watch the "1.8" hits he is getting
Overall I think that 1.8 offers a more diverse environment to pvp in.