So, only four classes, but each class has 9 specs, or souls. You make a setup by picking three of the souls, and allocating pts. This leads to a surprising amount of diversity, because while there's less diversity within a soul, you can mix and match at your leisure. The difference in the way these souls play is extreme; think Holy vs Disc Priest in WoW, and you've just described the difference between, say, the Sentinel and Purifier souls for the Cleric, ish. Now look again at the *9* different souls for each class.
So that's neat; the game really gives you a lot of variety to play with. Every class has souls that can either DPS, Tank, Heal, or Support (usually a combination of CC and heals), generally, each class having access to 3 of those archetypes. The slated update coming is releasing souls that will fill the gaps; Warriors will get a true Heal, Clerics a true Support, Mages a true Tank, and Rogues a true Heal.
So there's crazy diversity to how you can play the game, which makes someone like me very very entertained much longer. I've only leveled a Cleric to ~60 (max level), but have 5 separate spec setups that each feel quite different and fill different niches for what I'm after. Which means I've yet to really play with four souls.
With my Cleric, I have five specs that I'm mostly sticking to. One of them, the Defiler, a healing soul, does something I've never seen in any MMO to heal. It places 'links' on allies, and each link intercepts a %'age of the damage the target receives. Every time I heal, I place a buff on myself that absorbs that intercepted damage. So, my healing output may be a bit less than some other healers, but I reduce the incoming damage everyone is receiving. Additionally, every time I do damage, I have a chance to place a HAT on the targets of my links, and can proc that HAT whenever I want. The whole 'do damage to heal' or 'heal to do damage' mechanic is really neat, and I've seen in scattered games, but Rift really plays with with a few different souls. For example, the Cleric tanking spec tanks in part by healing itself and the group for a portion of the damage it deals.
Crafting is pretty typical for an MMO, but is intentionally designed such that by the time you're ready to leave an area and have collected mats and such, the gear you produce from crafting at level will be UPGRADES to your stuff. I remember in WoW, being level, say, 30, and having Blacksmithing at level, and producing lvl 20 gear. Not so with Rift; you'll upgrade your entire armor set if you keep crafting at level.
I would basically describe it as WoW for adults with a lot more diversity of *stuff*, and also, it's free to play. Like I said, the things you can pay for are extremely reasonable; the equivalent of a subscription (~15 a month) nets you a host of bonuses like +xp or +gold and such, and wardrobe purchases. If you want to spend money on the game, you can, if you don't want to, that's fine too. Trion has been very reasonable with what things cost, and it is the furthest from Pay2Win of any game I've ever seen. If you don't pay at all, you simply limit the number of bag slots you can have, don't have access to 1 soul for each class, and can't use the AH. That's about it, and that's hardly game breaking. Additional bag slots cost ~1 dollar, the souls are kind of pricy at ~15, and the AH comes with purchase of the expansion souls or with patron status, which is basically a subscription. It is not remotely Pay2Win. They recognize cosmetic purchases as cosmetic, and are really supporting the notion of 'micro' in microtransaction.
... with gigantic melancholies and gigantic mirth, to tread the jeweled thrones of the Earth under his sandalled feet.