Well, I'm not sure if "impressions" is quite the right word since I've actually beaten the game, but anyway, here are some of my thoughts on DKCTF, with a full review soon.
Donkey Kong Country Returns was the best 2D platformer of the last console generation, and Tropical Freeze is even better. Returns maybe suffered a little from "revival syndrome," that is to say, it felt like Retro Studios was so busy bringing the series back into the spotlight that it often felt more like a remake than a sequel (albeit a brilliant remake). But now that they've re-established the series, it feels like they've managed to give it their own personality.
The level design is some of the best I've ever seen in a platformer. Tropical Freeze may not be the most revolutionary platformer out there, but it certainly is a creative one.
It's also one of the hardest Nintendo games. Ever. As in, it goes toe-to-toe with the NES games that seemed to kick you while you were down. But unlike some of today's platformers that feel a little unfair (I'm looking your way, Super Meat Boy), almost all of my many (many) deaths felt more like player error, as opposed to unfair game design.
David Wise, the primary composer for the original DKC trilogy on the SNES, has also returned, which means the soundtrack is a substantial improvement over Returns (which didn't have a bad score, by any means). Tropical Freeze is less reliant on remixes than Returns was (again, revival syndrome), and has more original music. But the remixes are still there, of course. And this time, there are even a few remixes from the grand soundtrack of Donkey Kong Country 2.
Pretty much the only major drawbacks in the game are that it doesn't utilize the Wii U's capabilities in any meaningful way (if you play traditionally, the screen on the Gamepad is completely blank, it's only use is for off-TV play), and that the load times can get a little ridiculous. I suppose I wish there were more animal buddies again (once again, only Rambi the rhino returns, while Enguarde the swordfish remains absent despite the return of water levels). But I suppose that one's more of a preference than a complaint.
In short, DKCTF may be the best game on Wii U, if maybe not the best Wii U game (if that makes any sense).