Quick Review, i'm going to cover the stuff that makes Rift different from WoW first, the rest at the bottom is basically familiar MMO stuff.
Classes: Rift give you the option of 4 Archtypes [Mage,Warrior,Rogue,Cleric] . Each Archtype have 8 Souls. A soul is something like a "class" in which you can specialize in. You can combine 3 souls into a build aka "role" . WoW have a class and each class have 3 talent trees and you can make multiple "builds" [spending your talent points differently] and switch between them . Initially you might think this is the same thing, but it isn't.
To put it simply. Every Archtype have a soul that can heal, can tank, can support and can dps [to an extend]. Some Archtypes have better souls for certain things [i.e mages can't tank, but they get pets that can], but you can make a Rogue that tanks, you can make a Rogue that support heals, you can make a Rogue that has a pet and uses a Bow and you can make a Rogue that stealths and backstabs.....you can even make a Rogue that Stealths, places traps and Heal if you find a purpose for it. Likewise you can do similar things with the other archtypes.
The clincher is, you get 4 [after today's patch 5] slots for "builds" aka "roles" . You can switch between this any time, for free outside of combat. This implies you can go into a dungeon and switch to a ranged DPS build and on the boss fight turn into a support healer or tank , right there on the spot.
Rifts/Invasions : This is basically random "portals" that appear in the game world and spew out monsters that will attack anything in the area and eventually spawn mini armies to attack the towns in the zone. You can stop this by closing the rift. Closing a rift works like a Warhammer Public Quest, i.e. initially you ned to kill 5 mobs and it will go to "Stage 2" where you have to kill a second set of mobs and so on, eventually at Stage 4-5 a boss might spawn and then the rift is sealed. You get rewards for closing rifts which is a currency on its own. With the Rift currency you can buy gear and other stuff from special Rift Vendors.
You can see the Rifts on your map, so everyone know where to go. Once you enter a Rift you usually get a button that say "join public group" , so you can instantly join anyone that are with you in the rift. Most rifts need a group to seal, but depending on your class/build you can solo alot of Rifts too.
Every now and then, depending on the population of the Zone an Invasion will start. This is basically a Zone Wide Public quest. The invasion objectives will appear for everyone on the zone and usually consists of "close 30 rifts, stop 30 invading armies and kill the invading boss[es]" . During an Invasion Rifts will start to appear much faster and more of them will appear. The final invasion boss is usually some gigantic super boss and you need a raid-group to take him down in most cases. Again the public grouping system comes into play here.
There are different types of Rifts, you also get Raid Rifts that can only be opened by a Raid with the right material.
Anyway the rest:
Level cap : 50, there is very little grind to the level cap. I'd say it's similar to WoW Cataclysm lvl 1-60 .
Factions : There are 2 factions, Guardian vs. Defiant. Work same as WoW Horde vs. Alliance. You can roll both factions on the same server, but can't interact cross faction. Guardian theme is identical to Alliance [elves/dwarves/humans] while Defiant is not exactly "evil" like the Horde, but have different more "darker" races.
Questing : Identical to WoW. You run to a quest hub, grab quests, do them, repeat, next zone.
Crafting : Same as WoW with a few enhancements. You got gathering professions [foraging,mining etc] and got the crafting professions [armor/weapons/potions etc]. There are a "Works Order" system [crafting quests] which gives you "crafting currency" to buy special recipies with. This is similar to Aion's works order thing.
Combat : Identical to WoW, you have an action bar with abilities and you press them over and over to kill stuff
Dungeons: There is a 5-man dungeon about every 8-10 levels, just like in WoW. Every dungeon also got a more difficult version of it so you can repeat them at lvl 50 [same thing as a WoW Heroic] .
Raids : There's 10-man and 20-man raid content, i haven't done any of these, so can't comment, but sounds to work the same as WoW Raiding.
PvE Content : There are enough zones to get you to 50 comfortably. You will usually be able to skip one of the last zones entirely. The 2 factions got their own lvl 1-30 zones, then they are in the same zones to lvl 50. I'd say there are 1 or 2 uniquely interesting zones while the majority are stock standard medieval-fantasy zones [foresty,deserty,snowy,grassy]
There are a few exploration goodies like Artifacts and Puzzles. The artifact system is basically just random glowy items on the ground that you pick up, every set that you complete gives tokens . The puzzles are usually very well hidden and can be quite difficult, but gives nice epic rewards. You only do the puzzle once though.
Achievements: There are achievements as in all games these days.
Interface : Same as WoW, mini map, action bars, group/raid layouts ....same.
Modding : I don't think there are any mods [i don't use any] , so if you were relying on alot of mods in WoW then this might be annoying. There are however a whole macro language to write your own little scripts to automate things....
Graphics: Very good, much better than WoW .
Performance: Very good, this game don't need a super PC , can run on a laptop etc.
PvP : There's no Arena, but there are Warfronts which is identical to Battlegrounds in WoW and feels more like Scenarios in Warhammer. There are PvP and PvE servers. Only difference is PvP servers you can attack players in the open world, on PvE you need to turn on your PvP Flag first [so you can still fight in the open world, but only if you choose to do so] .
You get PvP ranks and PvP rewards. This works similar to WoW's PvP rewards. You can buy PvP gear with your PvP rewards and you get a PvP class aka "soul" which you can use in your build. The higher your PvP rank , the more you can spesialize in the PvP Soul.
You can join Warfronts anytime from anywhere, you gain XP while you are below lvl 50 [so you can level your character exlcusively doing Warfronts if you want to] and then switch over to PvP Ranks after you hit lvl 50. Basically you can be Lvl 50, PvP Rank 1-10 [not sure what the cap is] .
Guilds: Guilds get levels and can then gain enhancements per level. Similar to WoW guild system now. There are for some reason no guild bank (yet).
Servers: There's USA and EU server splits. However unlike WoW, you don't need a USA account to play on USA servers [or on EU servers] . You just need to switch your client .
Overall, the game is very well polished. The animations and UI works very well.
Other stuff:
They have just added a "Dungeon Finder" , i have not tested this, but it is suppose to work like the WoW one.
They also added a "cosmetic tab" , which i presume is similar to Lord of the Rings Online's system. Basically you can wear items with good stats but display different items [that doesn't necessarily have any stats on them] that actually look good.
I suppose only thing that is really missing is you can't fly...but matter of time i suppose.
