Nothing much has changed. Close combat weapons are melee weapons, which means they have no range (duh), and they either use the user's Strength or add to it. Some of them grant AP bonuses, and the weaker ones deal like 1 damage. Just look at the examples they give.
Yup, the classic power weapons are back, and each of them have their own uses. Not bad. As you can see, each of them have their own uses. Power axe grants a better AP than a power maul, but power maul grants better Strength. On the other hand, a power sword is the weakest of them, but has the best AP. I see people on Facebook complaining about how unfluffy this is - how can a power sword be more armor penetrating than a power axe? Well...a sword pierces better than an axe. Sure, an axe could probably cleave through armor better, but a sword is more accurate because you can pinpoint weaknesses and joints in the armor and penetrate those more easily than you would with an axe.
And for our Commissaars, we get a better chainsword! Woohoo!
All right Commisssars! We're all going to train under Lord Commissar Ciaphas Cain! We can deal an additional attack with it! Don't forget! Commisssar Cain, the Hero of the Imperium, has duelled with a Chaos Space Marine - one of the famous World Eaters at that - and prevailed (okay, he had Jurgen's help)! With his trusty chainsword! So don't underestimate this weapon! Not to mention, more Commisssars will be waving the chainswords atop their tanks and asking their drivers to move them forward so that they can hit the enemy with their trust chainswords!
Chainswords will OWN in 8th Edition! All hail Commissar Cain!
Keep in mind, these "weaker" melee weapons only deal 1 damage per hit. So you want to punch through tanks with melee? What do you take then?
Yup, the power fist is back, and it still multiplies your Strength by 2! So our Guardsmen will be hitting at Strength 6 with these babies! Keep in mind, the unwieldy rule is retained in a new form. As there is no more Initiative and all chargers get to swing first, the unwieldiness of power fists is now accounted for by subtracting 1 from the hit roll. Given how our Guardsmen's WS suck, we'll only be hitting with power fists on a 5+. That's...not good at all. Oh well. On the plus side, hitting at Strength 6, AP -3 and dishing out D3 damage is amazing. Just make sure you land those hits...I hope.
All Force weapons deal D3 damage, by the way. So another thing to take note for Grey Knights and Psykers. Cool.
Right, and they even have something for my beloved Imperial Knights! They actually included information on my Imperial Knights' Reaper Chainsword! It now deals a flat 6 Damage to whatever it Wounds. Keep in mind that Strength D no longer exists, but the Reaper Chainsword will still reap things in melee. 6 Damage per hit! Wow, that's pretty awesome. I bet the AP is also -3, so yeah. This is going to be so cool. I can't wait!
I know Ork players are enthusiastic about seeing the profiles of choppas, but it seems that they will have to be patient a bit longer.
Oh, and to confirm - pistols no longer grant you an extra attack in close combat. You can shoot pistols during the Shooting phase even if your unit is locked in combat, and that accounts for the extra attack in close combat during 7th Edition. This has been confirmed by the official Warhammer 40,000 page.