Recs.
Updated
SpecsUpdate
Pros
Pro Expansive RPG-style skill tree
While it may be difficult to take in at first the skill tree in Path of Exile is quite expansive allowing for many areas of the characters skills to be customized. The tree is so large there are numerous guides online on how to build specific optimized characters as well as an unofficial companion app for Android.
Pro Hundreds of possible character builds
There's a staggering amount of builds and skills you can try out in Path of Exile. There are 7 classes, 19 subclasses, 194 active skill gems, 107 support gems, and over 1000 skill nodes on the expansive skill tree. As a result, there are hundreds of possible combinations, allowing you to spend hours theory-crafting just to create the perfect build. Even if you don't feel like planning out a build from scratch, you can just look up one of the many guides online and get straight into the action.
Pro Completely free to download and play
Just install steam and download the game. No purchase required and the only thing locked behind paywalls is cosmetic accessories and inventory slots of which you can waste money on cosmetics, but you won't fall behind if you don't want to spend money.
Cons
Con Endgame can get really repetitive
It takes an exceptionally long time to get any wealth, useful items, or access to endgame bosses in this game. You endlessly farm the same maps, hoping you'll get lucky with a few good items, but that usually won't be the case, which can be really discouraging to keep playing. This is made worse by the fact that your character progression comes to a grinding halt near the upper 80s of character levels, requiring you to buy insanely expensive items to feel any progression at all. If you don't like grinding, you'll get quickly bored of Path of Exile.
Con Anti-experimentation for new players
The game heavily punishes any experimentation for new players. Unless you have near perfect understanding of late game and the various viable build-options you are more or less unable to experiment your way into viable builds (and the options for correcting mistakes are limited at best). So, unless you are fine with having to scrap a bunch of characters for being sub-optimal, you are more or less forced into following player-made guides to learn the game rather than through engaging with the game itself. This may or may not be a problem for you.
Con Rubberbanding disrupts play
Online play with melee classes may lead to some "rubberbanding" when latency causes the player's computer to desync from the server.
It should be mentioned however, that some users report having no such problems with the non-Steam version.
Con Very high learning curve
There's quite a lot to learn when starting to play Path of Exile. There are the mechanics, the crafting system, and the skill gem system. However, the most intimidating factor is the massive skill tree with over 1000 skill nodes, 6 classes and 19 subclasses, allowing you to create hundreds of unique builds. Unfortunately, creating a functional build is really difficult, taking hours of theorycrafting, so it might be better to stick to guides as you're starting out, unless you're fine with possibly messing up.
Con Clunky trading system
The western PC version of Path of Exile currently requires using an external site to find deals or sifting through scam attempts in the trade chat. After you find an item you want to buy, you need to message the seller, and if they respond, enter the same area as them to make a direct trade. There is no auction house, no mail, no automated trading posts, and to sell stuff you have to buy a premium stash tab via a microtransaction.