I've been playing through Alpha Sapphire, and so far it is amazing. I'll just post some of my experiences and thoughts here; feel free to disagree/discuss.
I started with Treecko, and spent a couple hours in the DexNav looking for a good Ralts (I couldn't find a Male Shadow Sneak one, so I settled for Misty Terrain) and a Brave Bird Taillow. This took me a couple hours, and sadly both of them had -Atk natures. Ah well, makes the game more challenging I guess. Roxanne was easily swept by Treecko, and then Brawly was defeated by Ralts and Taillow. Good Lord, OHKOing that stupid Makuhita with BB felt so good after it gave me pain in every RSE playthrough I have ever done. Point is, the first 2 gyms were really easy. It was sad to see that Granite Cave is no longer a proper dungeon; you just walk through a corridor to meet Steven.
Upon hitting Slateport, I spent a bit of grinding to evolve Ralts and get the other mons on my team to around level 20. I also entered Taillow in a Contest and got Cosplay Pikachu that went straight to the Box. I found the museum to be legitimately interesting; it's really neat how it teaches you about the real ocean. (I didn't know what 'hard water' meant until I went to the museum.) As for the battle against May on Route 110, she wasn't too hard apart from her Combusken, who required both Kirlia and Taillow to defeat.
I really like the design of Mauville City. The concept of an entire city that's indoors is really cool, and it's nice that the northern half of it has roughly the same layout as the original. Although some people say it's more of a mall than a city, I think it is indeed a city; it's just indoors. You have to remember that in Pokemon, 3 houses, a gym, a Pokemon center, and a Pokemart qualifies as a city, and so Mauville fits that criteria easily. It's true that there are a lot of shops, but there are areas in every real city in the world that are all shops. That doesn't make them outdoor malls! While on the topic of Mauville City, the hardest part of the game so far has been beating Wattson. Because I started with Treecko, Magnemite and Magneton walled my entire team. Luckily, there's a guy on the upper level of Mauville who sells you a Metronome for 1000P, and although competitively it's outclassed by Choice items, in-game it's quite useful. I ended up giving it to Grovyle and spamming Rock Smash, which eventually allowed me to win.
Route 117 and Verdanturf Town are largely unchanged from the originals, but the guy in Rusturf Tunnel gives you an Aggronite instead of HM04 now. Route 111 is also pretty much the same, complete with the Rock Smash boulders that block your path and annoyingly regenerate every time. To make matters worse, it seems that the wild encounter rate when smashing rocks has been boosted to 100%.
The Aqua Grunts were blocking the Cable Car, so I took a detour through Fiery Path to get around Mt. Chimney. Ace Trainer Wilton now has a Bagon instead of one of his other Pokemon (don't remember which). Sadly, Bagon is still only found in that remote area in Meteor Falls.
And then, at last, I made it.
To the area I was looking the most forward to.
Route 113.
The Route 113 remix absolutely blew me out of the water. GF did an amazing job with it. I could fanboy all day about the music, but since I'm terrible at describing songs, I'll talk about some other Route 113 aspects. The ground and grass are slightly greener than in the originals, which is sort of interesting. When you enter a battle, the surrounding trees are covered with ash, so they look a really cool light grey. Of course I had to claim the only secret base spot on the route; it's a very narrow hall, but I think I'll be able to make it work when I get more secret base stuff.
There is nothing I found interesting from Fallarbor Town to Meteor Falls, although Lanette changing 'Organize Boxes' to be 1st on the list is nice. Meteor Falls itself looked quite cool, successfully incorporating both rock and water into the design. The 3DS's graphics capabilities really give this area the attention it deserves.
The thing that has stood out for me the most has been Team Aqua. Archie in particular is my favourite NPC in the game; GF did a great job designing him. Every time I've encountered Team Aqua so far, I have felt that there is so much more to them beyond 'herp derp we're generic bad guys'. When the grunts blocking off Route 110 leave, they talk about how they want to stop at Mauville. You later see the same grunts commenting on how far it is to Mt. Chimney. Heck, even Archie seems to legitimately enjoy battling you, almost seeing you as his rival (I swept him with Gallade, but that's not the point). Every member of Team Aqua, even the Grunts, feels human to me. I am currently grinding before I enter there hideout in Lilycove, so I might edit this post later with more of my thoughts.
Finally, a question: Has the limit for the number of Pokeblocks you can feed to a single mon changed? I'm trying to get a Milotic, but I'm scared that I'll feed my Feebas the max number of Pokeblocks but still not have max Beauty.