Finally saw it last night and found my way here via Jasper's review (which I pretty much agreed with)
Some assorted impressions:
Warning: Spoiler! (Click to show)
I thought the new cast were great. Ridley in particular.
My favorite moments paying homage to the originals were when the new characters interacted with the old stuff (Rey's vision of the corridor on Cloud City after touching Luke's lightsaber gave me chills; Finn wrestling with the Falcon's gun turret was funny). I wished they'd exercised some restraint and left it to a few moments like this instead of giving us Episode IV's plot rehashed and countless straight visual quotations (like having a mini trench run complete with the gun towers...ugh).
Snoke is a horrendous name for a villain. What were they thinking?
For all the hype about practical effects there was still an awful lot of Bad CGI (Snoke and the Rathar tentacle monsters being the most egregious examples).
All of the weapon and vehicle effects were pretty great, though.
Retconning Hyperspeed so you can jump from/to anywhere you damn please (out of a hanger, right into planetary atmosphere) pissed off my inner nerd.
So many plot points occur in an absurdly convenient manner, often with the effect of making an apparently huge universe feel a lot smaller.
The 'Map to find Luke' was a really weak MacGuffin.
Rey's introductory scene where she's scavenging the derelict Star Destroyer was totally awesome (and I wish they used less of it in the trailer).
Out of the new characters I had the most issue with Finn (most people seem to have more problems with Rey / Kylo). Why? Well from the first scene his character is already set, there's no development or nuance in the way he abandons the First Order for the Resistance. He goes straight from not being able to kill villagers to willingly blasting away his stormtrooper comrades "because its the right thing to do" even though they are the only people and ideology he has known since childhood. He also manages to choose the most difficult and unlikely to succeed manner of defecting possible (freeing Poe and escaping a Star Destroyer) making his defection all the more jarring. I was expecting it to be something like he returns to Jakku or some other planet still a stormtrooper and the rest of his platoon gets killed off leaving him alone and conflicted, or he faces Rey / BB-8 and finds he can't kill/capture them and ends up helping them instead. I felt like the 'Stromtrooper gone rogue' character had tons of potential but didn't quite work (even though I thought Boyega was good).
Hamill looked great as a bearded Druid-like figure on his little Irish island.
I really, really don't want Rey to be Luke's daughter but I have a feeling I'll be disappointed.
I can totally see the sequel playing out with Luke training Rey while Kylo consolidates his power and searches for them, setting a confrontation at the end, ie. echoing the Empire Strikes Back story arc. I really hope they deviate from that though.