A flashy arcade like MMO with all the elements of the good.
I judge my MMO's by the amount of fun I can have that topples the obligatory grinds. For example, in WoW I had to grind my way to awesome gear with every new content patch, seemingly starting from scratch. Once I had the gear the real fun began. It's definitely fun to be able to do things that most could never imagine within the game.
With Rift, it's all about fun though. Sure you can grind, but really there is a large mix of fun. You can solo quest chains, or join world events by sealing very addictive rifts for excellent rewards, you can PvP with fresh gamestyles, or just go explore and gather items for crafting. If all else fails you can enjoy the brainless chats in public channels. If that all fails well you can reroll and try fresh classes that have interesting abilities and loads of combinations. Then after all that, there are places to explore and find seret looting areas and puzzles to solve in random areas. It's quite the thing. Oh yeah, and you can do 5 man dungeons too, there are plenty.
My complaints are few, such as being dismounted and getting a debuff when running from any level creature that increases damage. It makes for gathering mobs to kill VERY annoying. Other complaints are dry quest lines that don't tell much of a story or involve NPC's. Some imbalanced classes in PvP, and the Rift reward system is sketchy at best.
I don't enjoy crafting because I can always find more useful things from planar rewards or quest lines, and of course dungeon runs. Even just exploring and finding the secret loot will get you better gear than crafting would. Some areas seem inconsistent with quests and they just don't seem to flow very well at times, often I will find myself going all the way back to another area justto turn something in for little reward. But I guess I can stop at rifts on the way... you can never have enoug planarite.
The gameplay is a little rough around the edges. Mostly you stand and face a mob and trade damage while you press any number of buttons. Never really worrying or having a need to execute any type of mechanics. To make it more interesting you'd like to pull a few, and see if you can put them all down. All ou have to do is spam some buttons. There aren't any real tricks like say a rogue stun locking to get behind the target or stun charging and fearing to interrupt, or anything like that. Although I haven't tried every class, but I can definitely say killing mobs gets old fast. WoW has the upperhand here with great mechanics to each class, that make them fun to play. Rift seems dry and a trade damage fest no matter what class I have played so far.
What WoW doesn't have is the fresh and new, and the world events like Rift offers. It's easy to jump ship at the new and exciting things to try... but unless Rift can offer some more interactive combat, some rewarding crafting, and story telling quests where something interesting happens besides collectng and killing, then it's fun factor will die off eventually.
I'm going to enjoy it while I can, because I've done everything there is to do in WoW's ever diminishing community. I've been looking for a reason to quit WoW, so I hope that Rift gets better and better. It's addictive Rifts and rewarding levelling experience is great right now, and that's more than I can say for WoW's elitist raiding guilds and constant grinds with little rewards for a long time player. There just isn't much left you can do in WoW after 5 years of playing.
Rift is fresh and new, if it continues to improve it can be a great alternative to WoW's boring repetitious content patches and expansions. However if the mechanics don't change, WoW is going to reign supreme.