Despite being a game author with my own system to enjoy, I still love Dungeons & Dragons. It was the first RPG I ever encountered, and I own a copy of almost every edition ever released. I enjoy every edition, too, from the simple 0E/Basic all the way through to the tactically-minded 4E. I'm really excited for the new fifth edition. My wife agreed to run a campaign based on at least the Starter Set adventure. Normally I'm the GM, so not only getting to play a new edition of my second favorite RPG of all time (the first being my own Ingenium, of course) but actually being a player instead of the ref is a big change. The new Starter Set has a rule book, an adventure, a set of dice, and some pregenerated character sheets in the box. The box's contents have been covered in depth elsewhere, so I'll focus primarily on how I feel about the fifth edition rules themselves.
Attributes, Skills, and Proficiencies
One of the most interesting changes is in this area. Much like my own Ingenium, 5E now uses attribute checks for most everything that isn't covered by a specific skill. Want to try something related to Dexterity? Just roll a d20 and add your Dex bonus. Skills are a simple extension of that. They just add a small modifier to that roll. Same with Proficiencies. Proficiencies in 5E are particularly interesting, though, compared to previous editions. They can now apply to things other than weapons, such as Thieves' Tools. That reinforces a reoccurring theme with 5E: combat is no longer the sole focus of the rules.
Classes
In 5E classes got more streamlined than in 3E, and less crunchy than 4E. The loss of the powers mechanic from 4E is an interesting choice, and I feel that it opens the game up to more of a narrative experience. I can see where balancing classes for 5E could get problematic since it's less formula-friendly, but really, balancing a tabletop RPG is always problematic when it comes to clever players.
Races
Races are a lot simpler than in 3E or 4E, but they also feel a lot more “fluffy.” Building new races for 5E feels like building races for 2E, though a little more polished. I love this!
Spells and Spellcasting
Cantrips are at-will, whenever-you-feel-like-it spells. They don't take up a spell slot and don't count against the number of spells you can cast per day. This makes casters feel really useful, even when they're out of spells for the day. The spell lists feel a lot like AD&D 2nd Edition spell lists. The spells have a name, a component cost (verbal, somatic, and material), and a description, and that's about it. It's really flexible. While it does open the system to potential abuse, it feels a lot like AD&D, and that's a good thing in my book!
Advantage and Disadvantage
Probably the coolest core change is the addition of advantage/disadvantage. Instead of being a direct modifier to the roll, Advantage lets you roll a second d20 and take the higher of the two. Similarly, Disadvantage makes you roll a second d20 and take the lower of the two. This is roughly equivalent to a bonus (or penalty) of 3, but in terms of feel, the addition of a second die makes it just seem more dramatic.
Overall Thoughts
I love fifth edition. It reminds me of what got me into role-playing in the first place. I've already started converting content from Eiridia to 5E rules, and it just feels right. If you're on the fence, download the rules from the Wizards of the Coast website; they're free and unrestricted. It'll be worth your time, I promise!