Just got Skylanders Giants. I've only done the first 3 or 4 levels, but I have been impressed. I put the difficulty on hard to make it last longer, and even with 3 giants and 4 new characters (2 of them series 1 guys I got on sale), once or twice I had to dip into my emergency reserve of Spyro's Adventure characters. I also must say, Sprocket's figure pleasantly surprised me. Instead of being a plastic and dull figure like the official photos show, my version was actually chrome-ified, making it look more like she had battle armor, and there were some nice little details on her suit (may upload pics soon).
What I liked: Bigger and Better Levels
Better Graphics (Mostly, see below)
More memorable characters.
Awesome new battle arenas!
Giants, like big Hulks!
Some cool new normal characters, such as Sprocket.
Some fun new NPCs like Brock and Ermit.
Return of lots of familiar faces.
Flynn's customizable new ship.
Stores.
The cool light up features of the Giants/LightCore. Still not sure how they did it, I thought it would be done with light-conducting tubes, but instead, they light up even when only near or partially touching the portals.
What I Didn't Like:
New Voice Actors. Some captured the characters well, but others, not so much (looking at you, Stealth Elf)
All Characters have lines. This if fun for certain characters, but some, such as Wrecking Ball, just don't seem like they should have voices (and Sonic Boom with a bit of British accent? C'mon!).
Characters only say their catchphrase when activated. I preferred having multiple initial cries in Spyro's Adventure.
Old Characters Getting New Movements (Worse Graphics). While some characters look fine, others, specifically while talking, look like someone just moved their jaws up and down, making for some cheap animation (so far Prism Break and Bash seem the worst in this regard, but I haven't tried out all my old characters).
This is sort of half-in-half: The Hidden Treasure no longer works in the Hub, making it a lot harder to get easy upgrades or reset your characters. It also only activates once in a level.
So what are your thoughts on Giants?