I was underwhelmed by the playtest rules and about to write it off after the release of basic. Having seen the PHB and the DMG, I am neither positive nor negative on it, but ambivalent. There are positives and negatives. The first year of support is going to make up my mind. Right now, they are not doing a good job as I don't care about adventures.
Likes:
I like Backgrounds, Inspiration, Extra attacks tied to class, the bard, the battlemaster, the wizard traditions, and, for the most part, the Rogue, Warlock, and Circle of the Land Druid
My minor disappointments are
1) Races:
a) non-biological aspects of race in the race write-ups (e.g., Mountain dwarf armor proficiency). This gets in the way of races raised by other races and creates other cultural issues for specific campaigns. the non-biological stuff would have been better left to backgrounds and classes, imo.
2) More subclasses are needed
3) No Shaman, Warrior Mage, or Witch classes in the PHB. Some things are better served with classes and these three are fairly common archetypes
4) Expertise limited to Bard and Rogue and also hardwired into the classes. This makes a Bard or Rogue with Expertise in knowledge about Arcana better than a Wizard can ever be. The same goes for Religion and clerics. Furthermore, it prevents a fighter that grew up in the outdoors and used to model a wilderness warrior can never be as good at outdoor skills as a rogue with the same skills that started off as in the city and then later picks up wilderness skills (and some people keep saying to use the fighter as the non-spellcasting ranger wilderness expert by picking up an appropriate background and wearing light armor), etc.
5) Jack of all Trades: Personally, I have never liked the Jack of All trades for the Bard. I don't mind it as an option, but I don't appreciate it hardwired into the class.
6) Several of the variant backgrounds and background specialties were not fleshed out as their own backgrounds, because I would expect different skill proficiencies, tool proficiencies, and/or features (yeah, it is easy to change, but still)
7) No skill point variant in the DMG (not that it would hard to implement, but, in my opinion, a serious omission).
8) No DMG variants to replace simple and Martial weapons with AD&D weapon proficiencies and/or (Weapon Groups 2e fighter handbook/PO: Combat and Tactics/ 3e Unearthed Arcana)
9) First level spellcasting classes not granting cantrips only at first level. I have no problem granting a bonus first level spell or two to those starting out, but I don't like someone multiclassing into one of those classes gaining first level spells. I want them limited to cantrips for one level- have to learn the basics and crawl first. This is part of my dislike for the multi-classing rules.
10) Several of the classes not getting their subclasses at first level. Who trained the fighter? A gladiator? A bodyguard? a pirate on a ship? A swashbuckler? A tribal warrior whose people don't have armor and rely on maneuvers rather than rage?. Backgrounds are a good start, but this, in my opinion should affect armor proficiency and starting weapons in addition to fighting style (this is why I like 2e kits (in concept) and 3e classs variant better than 5e subclasses). Yeah, one could house rule giving a class something along the lines of the Barbarian or Monk when not wearing armor (and even removing certain armor types and requiring training rules to gain back the lost armor proficiency), but it would have been nice to have this built into the class or have provided a Light Armor Fighter class with swashbuckler, musketeer, duelist, etc. as subclasses that fills the gap between the Rogue and standard fighter.
Similarly, I am of the opinion, that the Land should be even more important than it is for Circle of the Land Druids. It should have more impact on the Druid at first level as in Mongoose's Quintessential Druid Web Enhancement- Lords of Terrain for 3e and on their spells than the circle bonus spells (I think Roger Moore did a better job in his web article on Environmental druids for 2e)
11) Not breaking AC down in a 3e fashion
My major disappointments, however, are the Cleric, the Monk, guidelines for customizing classes, the multi-classing rules, and
The cleric,in my opinion, goes back to the suck that was the non 2e priest of specific mythoi/specialty priest of early editions or pre-3e. Despite being better balanced than the default 3e cleric, I also still think it is terrible when compared to the 3e cleric if using spontaneous divine casting option from Unearthed Arcana, the DMG tailored spell list variant, and having the cloistered cleric. Access to the entire cleric spell list, every cleric getting turn undead, every cleric having at minimum medium armor and shields all without regard to deity should have died along time ago. I am not even impressed with many of the domain abilities or the divine intervention mechanic. I think that in addition to domains, it needed something similar to Warlock chain, pact, tome, but scholarly (no armor), martial, and something in between. As disappointing as I find the cleric, I don't know that I want to "fix" it for another edition.
The Monk: I have never been against having a monk class in D&D (see Will Shetterly's Witch Blood). However, I was disappointed to see many default abilities from 1e and 3e carry over to default abilities for all monks in 5e rather than being moved to a subclass where they belong.
Customizing a class: I, wish, there was more information on customizing classes and hard examples. I have done it over enough editions, but I know many DMs for more hard examples would be useful. During 3e, many people refused to use customizing a class from the 3.0 PHB and DMG, because they felt there were not enough hard examples of what things were worth when swapping one thing out for another or adjusting a classes skills, skill points, hit die, armor proficiency, weapon proficiencies. Among the people I know for whom more examples would beneficial are two people that started as 3e DMs for other groups before joining my 3e group as players.
Multi-classing: The multi-classing rules does not work for me- especially, if learning from another character while travelling between adventures when there is not a lot of downtime. Multi-classing grants too much for my taste. It was an issue for me as well in 3e, but with 3e Armor Feats, Weapon Feats (especially, if using UA Weapon groups) a feat that grants 3 0-level spells and no first level spells, it was much easier to house rule multi-classing into something more acceptable.
All the above stated, I think 5e is a better place to start house ruling than other editions to meet my needs as it would need less. However, I don't know that I want to heavily house rule/rewrite the cleric for a fourth time nor am I sure what to do fix my issues with multi-classing (which I prefer using as a last resort after classes and subclasses)