You don't have to pick a specific class, as your character's role and level are based on what gear you have equipped. Playing as a high-damage DPS or a beefy tank is just a matter of collecting or crafting gear that boosts your attack or defense rating. Switching between the two is easy, and The Secret World lets you save your various "costumes" so you're given a lot of free range to experiment and play around with various builds. It's a nice and highly flexible system, and I enjoyed that I wasn't locked to performing a specific job with no room to maneuver.
One important thing to note about The Secret World is that, for an MMO, I encountered very few bugs. All of the core mechanics worked as intended and felt balanced, and while the game occasionally crashed for me when I was using the in-game web browser, technical issues appeared to be few and far between. A mission or two may require you to change instances in order to get them to work right, but for the most part, The Secret World is a solidly put together game.
As polished as the The Secret World is, though, there is an issue of replayability. Given how easy it is to switch around classes and abilities with just one character, you may find that there's not much incentive to start up any alternates from a different faction. There are also very few faction-specific missions or plot points in the first dozen or so hours of play, and you don't have to switch allegiances to be able to learn more about the game's core story or lore. You can replay most quests to gain more experience and rewards, but once you've played through an exorcism quest as a member of one secret society, you may not feel like playing through it again as a member of another. Thankfully, there's more than enough content that you won't feel the need to fire up the character creator again.
Currently, PvP is lacking in depth. There's only three arenas and two modes to choose from, and you give up your custom made character to play a faceless soldier to fight against other faceless soldiers from rival factions. Stats are automatically balanced so everyone's on the same footing, meaning you don't have to worry about a few all-powerful players wrecking everyone's day. The fights feel more like generic deathmatches than epic battles for your faction's supremacy. Factions do get a global stat bonus depending on how successful their members are at taking and holding key objectives, but the differing arenas can change hands so quickly that, regardless of whether you participate, chances are you'll have a faction bonus up all the time anyway. If you're really into PvP, you'll get a kick out of the constant tug-of-war, but for everyone else, there's not much of a draw.
The Secret World delivers an excellent MMO experience with a flexible character design system and challenging puzzle quests, and is only hampered by weak PvP and a lack of replay value. Whether you're new to MMOs or have been playing them for years, there are not many reasons not to give its Lovecraftian mysteries and global conspiracies a chance.
Bottom Line: With a unique setting, immersive story and open-ended character system, The Secret World offers up a great MMO experience that's only held back by problems with replay and weak PvP.
Recommendation: If you're new to MMOs or have been playing them for years, The Secret World delivers a gameplay experience that's accessible, engaging and most importantly, fun.