(I'm not sure what you're talking about with the opening: that's, um, how every single Star Wars movie starts? What was different here?)
Um... basically my comment is 'squeeeeeeeeeee!'. There aren't many movies I want to see twice in cinema - this is one of them.
One thing I really liked (on thinking about it) was the new protagonist trio. They managed to be at the same level as the protagonists of A New Hope, without being carbon copies of them. Without spoilers, I can say:
-A New Hope featured a naive farmboy who lost his family, a disreputable smuggler, and a princess who immediately got captured. All three are at a pretty low ebb in the early parts of the movie, and we get to see their struggle to actually impact the world around them.
-The Force Awakens trio (actually it's a bit more complicated than that, but still) also all hit that level of 'low' early on. None of them start the main plot in positions of strength, which makes it interesting to follow them climbing back up. But while, arguably, one character is similar in summary to one of the original three, the other two fall into entirely new categories.
-In stark contrast, the four protagonists of The Phantom Menace are: a pair of galaxy-renowned Jedi, a ruling queen, and a superpowered slave boy. While Qui-Gon, Obi-Wan, and Amidala all get into difficulties, none of them lose their positions of power. The Jedi just needed to find a ship; Amidala just needed to reach Coruscant. Anakin is the only one who's ever 'weak', but he is immediately told he'll be rescued by deus ex Jedi.
Compare the prequel's 'bother, our ship is a bit broken, we'd better stop to fix it' with ANH's 'my family are dead and the planet I was supposed to go to is dead and now my mentor is dead too!'; which one sounds like a more interesting character arc? If you said the second one, you're right - and that's the sort of thing you'll see in The Force Awakens.
(Though not those specific troubles. Obviously.)
I loved the various ways the film paid homage not just to the original movies - lots of lines and visuals in there - but also to the dear departed EU. Unnnnfortunately they're all spoilers. ;) But I spotted things that felt like references to everything from the X-Wing books (a certain character is clearly ex-Rogue Squadron) to... er, what was the last thing we had? That, anyway. ^_^
(There were also a lot of older actors who got inexplicable closeups; I really have to wonder if they were original/prequel actors. If you watch it, look for the woman who tends someone's injury; who is she?)
As Superfluity says, it was also gorgeous. You could absolutely tell that the outdoor sequences took place in actual, physical environments, and it did wonders. A few of the 'matte paintings' (which I assume were digital) looked a bit off, but other than that: stunning.
So what didn't I like? Mostly three things:
1/ Sadly, the X-wing sequences were less good than they should've been. Partly because they were the most obviously CG (even if they weren't CG!), and partly because... well, remember how in ANH you actually felt bad when Porkins and Biggs died? Yeah, I can't name any of the pilots in this one (other than one we'd already met), and have no idea which of them survived the film. The way we flashed between them felt like I was supposed to care, but I... didn't. (Makes me wonder if there's a deleted scene where we meet the squadron.)
2/ There's one sequence which seems to indicate you can see planets in other star systems in real-time from the ground. That's... wrong. :-/ (The alternative is that there are seven worlds in close proximity in the same system, which would work, but doesn't seem to be what they were aiming for.)
3/ There's no easy way to say this, but... one character is totally Voldemort, in his bald-snake-face period. I don't know what he's doing there, but I'm sure it isn't good.
Overall? I said in advance that I wanted this to be to ANH what Jurassic World was to JP.
It isn't.
It's better.
hS
PS: And I am ridiculously pleased that it's possible to summarise about half the plot in one incredibly spoilery word. ~hS