I start this thread with no trollishness or malice, but after reading a thread in which one poster was lamenting the return of save-or-dies and Vancian casting, I have to ask: why are 4e players so interested in 5e?
As far as I can tell, 4e D&D diverged significantly from previous editions of D&D, in essence putting the game on an easier difficulty setting. (No snark intended.) Gone was the resource management and brutally unforgiving combat of earlier editions, instead replaced by balanced encounters. There are a whole host of changes to the game that 4e players generally see as positive that are a drastic move away from traditional D&D.
• Hit point mechanics. The introduction of healing surges and overnight healing negated the resource management aspect of HP. With players able to heal themselves (in combat, of all things) and a large pool of "reserve HP" to draw from, it was the expectation that the PCs would start their combats at full health. This greatly contrasted with previous editions where players were expected to manage their HP and healing over the course of an adventure (ignoring the 3e wands of cure light wounds nonsense).
On top of this, the introduction of "easy healing"--minor action ranged healing that did not consume resources outside of the combat encounter and healing that triggered off another action (such as an attack)--exacerbated the divergence of healing mechanics until they no longer resembled traditional HP models.
• AEDU power structure. Prior editions of D&D did not have a power structure at all. There were classes, some of which cast spells, some of which received sort-of spells (such as a paladin's remove disease), some that received skills (such as a thief's hide in shadows), and some that received passive bonuses. It was, in essence, a messy system. (And if you go back far enough, there weren't skills at all!) 3e attempted to remedy this by giving everyone skills and allowing them to access feats (some of which granted passive bonuses, some of which modified actions, and some of which offered new actions).
It was still a mess. A imbalanced mechanical nightmare of a mess, but, at the same time, a lovely, wonderful mess of which I have fond memories.
4e took that mess and streamlined it significantly, for better and for worse. Rather than having some players with "powers" (such as spells or smite evil) and those without, 4e gave everyone powers, and the developers made sure that everyone had about the same amount. They also tried to eliminate the fifteen-minute workday by giving everyone renewable powers--no more forcing the fighter and rogue to rest after one fight because the wizard and cleric cast all their spells.
This was a complete departure from prior editions. It had its benefits, of course, but it was a completely different beast.
• Non-Vancian Spellcasting. This ties in with the above. Some people love Vancian spellcasting, some people hate it. D&D, however, has always had Vancian spellcasting. There were problems with it; balance issues cropped up because spellcasters were potent at the beginning of the day and their power waned as they expended their high-level spell slots and were forced to rely on weaker and weaker spells (and eventually their crossbows). 4e attempted to remedy this by leveling out the power curve. Once a spellcaster (or, indeed, any other class) expended their daily resources, they were weaker, but not without power, as they had backup spells at their disposal: at-will powers and encounter abilities.
Coupled with this was the drastic reduction in spellcasting power. While spellcasters needed to be powered down in 3e--as certain designers removed the limitations of spellcasting in previous editions and drastically increased their power and versatility--4e did this by ripping the guts out of the Vancian spellcasting system, as noted above.
• No save or lose effects. They exist in the most technical sense possible. Usually, you must fail several consecutive saving throws to die, which puts the odds firmly against the effect sticking. Compounding this are the plethora of effects that allow you to make a saving throw to throw off said effects. Certain builds (orb of imposition wizard) could stack huge penalties to saving throws and stunlock monsters, but the danger of a medusa's gaze was, shall we say, neutered from previous editions.
• Treasure parcels. Depending on the edition of D&D that you are playing, the treasure gods have a significant impact on your character's power. In pre-3e, you rolled for treasure all the time. In 3e, you rolled for treasure but could have a spellcaster craft your magic items if you really wanted that +3 sword. In 4e, you give the DM a wishlist and, if you didn't like what he gave you, you could break down magic items and convert them to what you really wanted in a short period of time.
Long gone were the days of gambling on the loot tables and getting something you didn't want. You had only to ask and you would receive. Everything was precisely configured to give you want you wanted, when you wanted.
That last sentence summarizes 4e versus prior editions of D&D: you get what you want. And for the 4e players, 4e does what they want. It gets rid of the pesky D&D tropes that bothered their games. No more cleric healbots. No more sitting in a swamp for three days waiting to heal. No more wizards running out of spells. No instant death. Heck, no alignment restrictions or paladins falling or clerics losing their spells.
It seems that 4e is everything that 4e players wanted. On the other hand, 3e was not everything that I wanted. 3e was a mess that I would like to see simplified and clarified. Thus, my edition of choice needs revising beyond what Pathfinder offers. I am invested in 5e because 3e wasn't all it was cracked up to be.
Thus, it seems that 4e must not have been what 4e players want, or else they wouldn't be invested in 5e. So my question to you, 4e players, is what you didn't like with 4e that you hope to see in 5e?