- The streamlined core mechanic: d20 + ability mod + proficiency bonus, with or without advantage/disadvantage. This makes the game so much easier to run. Fast, simple, and fun.
- Equipment packs. About time. (Can't remember if 4E had this or not)
- Pretty good balance of detail/simplicity. We play with minis more often than not, and it's refreshing to have this playstyle be well supported, but also fast and simple to adjudicate. Combats run well and I'm very happy with this.
- Backgrounds (the roleplaying cue parts). My players don't seem to have latched onto this at all, but for my PC, it was great to have the handful of cues from Trait/Ideal/Bond/Flaw to help me figure out how my character would act.
- Familiar but new. The game is without a doubt D&D, but every time I crack open one of the books I find a new twist on something. This is really cool because it's like rediscovering D&D all over again. Examples: add DEX mod to ranged weapon damage (even crossbows), partial move/act/partial move is something everyone can do without fancy feats, the concentration mechanic, the attunement mechanic, magic item and spell mechanics, etc. I haven't found many of these tweaks that I wouldn't be able to classify as improvements, although the way the sleep spell works is a bit clunky.
- The game's been out for a year and there are no official digital/web tools. Character generation isn't extremely cumbersome, but it's time-consuming and complex enough that an app like the 4E character builder would be welcomed with open arms (minus the monthly subscription fee of course). The SRD is out now, so we have 5eSRD.com and people can at least start building stripped-down versions of these tools, but they won't legally be able to support all the options in the PHB. It makes me very sad because these things would make my life so much easier as a DM/Player of the game. P.S. - Fantasy Grounds, the only application that is fully licensed to have all the PC options, and meant for online play, is one of the worst pieces of software I've ever had the displeasure of trying to use. It makes the 2E CD-ROM suite look like sleek Apple software.
- Character creation as outlined is a bit goofed up and can necessitate some backtracking to re-select skills that are duplicated and that sort of thing. I think it should go Abilities > Race > Background > Class. This is kind of a head scratcher, like, how'd they screw this up? Also, character creation takes way too long. It would be nice if they got you up and running more quickly. In my experience it seems like it can take about 30-60 minutes depending on if you have to pick spells or not.
- The cover art SUCKS. On the whole, I think the interior art is mostly good, but the cover art is too monochromatic and lame. The Monster Manual is the least offensive of them, but the color scheme of the PHB cover honestly makes me want to vomit. If they ever release PDFs of the core books, the first thing I'm going to do is make myself some POD versions with decent cover art. Maybe if we're lucky they'll make some special edition sets with better covers.
- Backgrounds are cool to flesh out the character, but I think they went a bit overboard with them. Having skills, languages, equipment, and features tied to background make them too bulky and too much of a difference maker to discard completely. If background was just the roleplaying bits, Ideal, Flaw, etc. then the players who wanted it could use it and the players who didn't care could just generate their character faster. I'd be interested in ideas for a replacement system for backgrounds that is faster and balances with characters that have the regular by-the-book backgrounds. Maybe just choose a feat instead?
- The characters have too many class features. You can't really give too many magic items because they would just become way too goddamn powerful. I guess this is why they limited attuned items to 3. I'd rather have more goodies to acquire in play, and less abilities that you get automatically when leveling.
In summation, I guess you could say I love the gameplay, but not a huge fan of the complexity of characters. I like it to be possible to generate a character in 10 minutes or less, and I like the characters to get cool stuff through adventuring, not just have a billion built-in class abilities.