Early Access in the context of this game means being able to play what is essentially a demo with data transfer. But not free.
The import impressions thread for SAO:HR is probably going up on Thursday, when the game is officially released. That said, if you preordered the game on Japanese PSN, you could start playing a version of the game containing the first chapter (10-15 hours) since Thursday last week (details). The data can be transferred to the full game.
Since I finally caved in, I decided to share some impressions from the first few hours with the game, if anyone is thinking about the digital preorder to play it early. I'm still only level 8 (maximum level in the EA is 20).
Story
So far it's a standard SAO fare. While the premise of the story is quite interesting, if you're allergic to waifus, stay away.
Graphic & Performance
I played a bit of Re: Hollow Fragment right before buying HR and I have to say that the new game is an enormous step up. Fields are much bigger and more detailed. I believe the game runs in locked 30 fps in the town and 60 fps in the field. At least that's what the streamers are claiming. I only know that it feels much smoother in the field, so I'm willing to believe it.
You can see armors and weapons on the MC (not sure about other characters, haven't given them anything yet) and all would be great if not for the fact that character models are by far the worst thing in the game, graphic wise. That said, they're still a step above HF, so if you didn't mind that, you'll be fine.
Some cool touches include a day and night "cycle" (I don't think it can change when you're on a map) and different weather types.
That said, while HF doesn't feel like it has the PSP legacy, like HR, don't come expecting an AAA production levels on the visual side. It looks decent, but still like a budget game compared to bigger Western titles.
As for the performance, on the PS4 the framerate feels stable, which is good in a game where a lot of the combat involves precise timing. I had one weird drop so far, but it felt more like a bug than a result of many objects on screen.
I haven't personally played the Vita version, but from what I've seen, the framerate during the raid (multiple parties at once) battle with the boss of the first chapter is quite choppy.
UI, Gameplay
While some elements of the UI are the same as in HF, you can't assign as many easy access shortcuts, which is a bit annoying. The developers went all in with giving you a shortcut palette like in a regular MMO. Sadly, since you move around it with the d-pad, and lose access to the skills assigned to the circle button, I don't find it very useful for active combat skills - it's okay for things with longer cooldowns and buffs though.
Another change (or maybe I haven't played enough HF to get to it) is allowing you to set 4 sword skills per button (Triangle/Circle) together with inputs, something similar to the Tales series. One skill for neutral, forward + button, forward twice + button, circle with the stick + button. I'm sure more advanced players will be able to use it to the fullest, but at this point I'm a bit too busy with other things during combat.
What's neat is that different directional inputs with your regular attack result in different moves. Also, you can link multiple swords skills if you get the timing right, although I haven't tried it extensively just yet.
AI
AI of your 3 NPC partners is dumb as a rock. This complained appeared over and over in the 2ch threads about the EA and after playing for a while I have to agree. The game has the AI training system from HF, where you can praise actions so that AI does them more, but the problem lies with the characters being way too slow to react to your commands (and with the amount of AoE attacks they should react fast). If you try to take on enemies above your level, be prepared to be the only one alive during the most of the fight.
Bugs
The game currently has quite a few bugs, most of which are related to characters/enemies getting (rarely) stuck in geometry or not reacting to attacks. There is a level 95 (I think) boss on the very first field and some people were already able to beat it on low levels using exploits. On one of the streams I've seen one of a monster's adds, which you had to kill before you could damage the main enemy, being stuck on the other side of a wall, so the player couldn't get to it and had to run away.
Hopefully these will be fixed in a day 1 patch.
All in all, as negative as some of the above might sound, I'm enjoying HR much more than the beginning of Hollow Fragment and Lost Song, despite the game feeling like an upgraded sequel to the former. The combat feels faster and more action oriented and sword skills finally have the "umpf" (at least more than in HF).
Videos
If you want to see the game in action, I recommend watching videos in Havian's twitch archive - that's what I did. There are many more on Youtube, since there's quite a few people playing this version, including players commenting in English.